Ping.

On Thu, Jul 31, 2014 at 09:39:21AM +0200, Marek Polacek wrote:
> One of the prerequisites to moving the default from gnu89 to gnu11
> is that we need both -Wc90-c99-compat and -Wc99-c11-compat options.
> This patch implements the former.  Its purpose is similar to
> -Wtraditional - that people who build code in C99/C11 mode can easily
> check whether the code uses something outside C90.  Since
> __extension__ disables this warning, features that are properly
> conditioned are fine and not warned about.
> 
> As I said privately, it turned out to be convenient to reuse
> pedwarn_c90 - the patch now mostly removes code.  Earlier I defined
> a special function, but that rendered pedwarn_c90 unused.  Another
> benefit I see is that if we ever add pedwarn_c90, we have
> -Wc90-c99-compat handled for free.  And obviously, defining yet
> another warn/pedwarn function would be confusing.
> 
> A few issues: currently we don't warn (in -std=c90 -pedantic mode)
> about the usage of __func__ and _Pragma (possible others - va_copy?).
> I'm hoping this is not that important though.  For restrict/inline,
> in GNU90 mode we just don't compile the code at all (unless we use
> __restrict and similar), and -Wc90-c99-compat does not warn about those.
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
> 
> 2014-07-31  Marek Polacek  <pola...@redhat.com>
> 
>       PR c/51849
> gcc/
>       * gcc/doc/invoke.texi: Document -Wc90-c99-compat.
> gcc/c-family/
>       * c-opts.c (sanitize_cpp_opts): Pass warn_c90_c99_compat to libcpp.
>       * c.opt (Wc90-c99-compat): Add option.
> gcc/c/
>       * c-decl.c (build_array_declarator): Remove check for !flag_isoc99.
>       Call pedwarn_c90 instead of pedwarn.
>       (check_bitfield_type_and_width): Likewise.
>       (declspecs_add_qual): Likewise.
>       (declspecs_add_type): Likewise.
>       (warn_variable_length_array): Unify function for -pedantic and -Wvla.
>       Adjust to only call pedwarn_c90.
>       (grokdeclarator): Remove pedantic && !flag_isoc99 check.  Call
>       pedwarn_c90 instead of pedwarn.
>       * c-errors.c (pedwarn_c90): Handle -Wc90-c99-compat.
>       * c-parser.c (disable_extension_diagnostics): Handle
>       warn_c90_c99_compat.
>       (restore_extension_diagnostics): Likewise.
>       (c_parser_enum_specifier): Remove check for !flag_isoc99.  Call
>       pedwarn_c90 instead of pedwarn.
>       (c_parser_initelt): Likewise.
>       (c_parser_postfix_expression): Likewise.
>       (c_parser_postfix_expression_after_paren_type): Likewise.
>       (c_parser_compound_statement_nostart): Remove check for !flag_isoc99.
>       * c-tree.h: Fix formatting.
>       * c-typeck.c (build_array_ref): Remove check for !flag_isoc99.  Call
>       pedwarn_c90 instead of pedwarn.
> gcc/testsuite/
>       * gcc.dg/Wc90-c99-compat-1.c: New test.
>       * gcc.dg/Wc90-c99-compat-2.c: New test.
>       * gcc.dg/Wc90-c99-compat-3.c: New test.
>       * gcc.dg/Wc90-c99-compat-4.c: New test.
>       * gcc.dg/Wc90-c99-compat-5.c: New test.
>       * gcc.dg/Wc90-c99-compat-6.c: New test.
>       * gcc.dg/wvla-1.c: Adjust dg-warning.
>       * gcc.dg/wvla-2.c: Adjust dg-warning.
>       * gcc.dg/wvla-4.c: Adjust dg-warning.
>       * gcc.dg/wvla-6.c: Adjust dg-warning.
> libcpp/
>       * lex.c (_cpp_lex_direct): Warn when -Wc90-c99-compat is in effect.
>       * charset.c (_cpp_valid_ucn): Likewise.
>       * include/cpplib.h (cpp_options): Add cpp_warn_c90_c99_compat.
>       * macro.c (replace_args): Warn when -Wc90-c99-compat is in effect.
>       (parse_params): Likewise.
> 
> diff --git gcc/gcc/c-family/c-opts.c gcc/gcc/c-family/c-opts.c
> index 3f8e6e6..43a8b9d 100644
> --- gcc/gcc/c-family/c-opts.c
> +++ gcc/gcc/c-family/c-opts.c
> @@ -1295,6 +1295,7 @@ sanitize_cpp_opts (void)
>    cpp_opts->unsigned_char = !flag_signed_char;
>    cpp_opts->stdc_0_in_system_headers = STDC_0_IN_SYSTEM_HEADERS;
>    cpp_opts->warn_date_time = cpp_warn_date_time;
> +  cpp_opts->cpp_warn_c90_c99_compat = warn_c90_c99_compat;
>  
>    /* Wlong-long is disabled by default. It is enabled by:
>        [-Wpedantic | -Wtraditional] -std=[gnu|c]++98 ; or
> diff --git gcc/gcc/c-family/c.opt gcc/gcc/c-family/c.opt
> index f427da1..b62bac1 100644
> --- gcc/gcc/c-family/c.opt
> +++ gcc/gcc/c-family/c.opt
> @@ -291,6 +291,10 @@ Wbuiltin-macro-redefined
>  C ObjC C++ ObjC++ Warning
>  Warn when a built-in preprocessor macro is undefined or redefined
>  
> +Wc90-c99-compat
> +C ObjC Var(warn_c90_c99_compat) Warning
> +Warn about features not present in ISO C90, but present in ISO C99
> +
>  Wc++-compat
>  C ObjC Var(warn_cxx_compat) Warning
>  Warn about C constructs that are not in the common subset of C and C++
> diff --git gcc/gcc/c/c-decl.c gcc/gcc/c/c-decl.c
> index 2a4b439..b1c5862 100644
> --- gcc/gcc/c/c-decl.c
> +++ gcc/gcc/c/c-decl.c
> @@ -3968,16 +3968,13 @@ build_array_declarator (location_t loc,
>      }
>    declarator->u.array.static_p = static_p;
>    declarator->u.array.vla_unspec_p = vla_unspec_p;
> -  if (!flag_isoc99)
> -    {
> -      if (static_p || quals != NULL)
> -     pedwarn (loc, OPT_Wpedantic,
> +  if (static_p || quals != NULL)
> +    pedwarn_c90 (loc, OPT_Wpedantic,
>                "ISO C90 does not support %<static%> or type "
>                "qualifiers in parameter array declarators");
> -      if (vla_unspec_p)
> -     pedwarn (loc, OPT_Wpedantic,
> +  if (vla_unspec_p)
> +    pedwarn_c90 (loc, OPT_Wpedantic,
>                "ISO C90 does not support %<[*]%> array declarators");
> -    }
>    if (vla_unspec_p)
>      {
>        if (!current_scope->parm_flag)
> @@ -4891,10 +4888,9 @@ check_bitfield_type_and_width (tree *type, tree 
> *width, tree orig_name)
>    if (!in_system_header_at (input_location)
>        && type_mv != integer_type_node
>        && type_mv != unsigned_type_node
> -      && type_mv != boolean_type_node
> -      && !flag_isoc99)
> -    pedwarn (input_location, OPT_Wpedantic,
> -          "type of bit-field %qs is a GCC extension", name);
> +      && type_mv != boolean_type_node)
> +    pedwarn_c90 (input_location, OPT_Wpedantic,
> +              "type of bit-field %qs is a GCC extension", name);
>  
>    max_width = TYPE_PRECISION (*type);
>  
> @@ -4925,52 +4921,27 @@ static void
>  warn_variable_length_array (tree name, tree size)
>  {
>    int const_size = TREE_CONSTANT (size);
> +  enum opt_code opt = (warn_vla == -1 && !warn_c90_c99_compat)
> +                   ? OPT_Wpedantic : OPT_Wvla;
>  
> -  if (!flag_isoc99 && pedantic && warn_vla != 0)
> +  if (const_size)
>      {
> -      if (const_size)
> -     {
> -       if (name)
> -         pedwarn (input_location, OPT_Wvla,
> +      if (name)
> +     pedwarn_c90 (input_location, opt,
>                    "ISO C90 forbids array %qE whose size "
> -                  "can%'t be evaluated",
> -                  name);
> -       else
> -         pedwarn (input_location, OPT_Wvla, "ISO C90 forbids array whose 
> size "
> -                  "can%'t be evaluated");
> -     }
> +                  "can%'t be evaluated", name);
>        else
> -     {
> -       if (name)
> -         pedwarn (input_location, OPT_Wvla,
> -                  "ISO C90 forbids variable length array %qE",
> -                  name);
> -       else
> -         pedwarn (input_location, OPT_Wvla, "ISO C90 forbids variable length 
> array");
> -     }
> +     pedwarn_c90 (input_location, opt, "ISO C90 forbids array "
> +                  "whose size can%'t be evaluated");
>      }
> -  else if (warn_vla > 0)
> +  else
>      {
> -      if (const_size)
> -        {
> -       if (name)
> -         warning (OPT_Wvla,
> -                  "the size of array %qE can"
> -                  "%'t be evaluated", name);
> -       else
> -         warning (OPT_Wvla,
> -                  "the size of array can %'t be evaluated");
> -     }
> +      if (name)
> +     pedwarn_c90 (input_location, opt,
> +                  "ISO C90 forbids variable length array %qE", name);
>        else
> -     {
> -       if (name)
> -         warning (OPT_Wvla,
> -                  "variable length array %qE is used",
> -                  name);
> -       else
> -         warning (OPT_Wvla,
> -                  "variable length array is used");
> -     }
> +     pedwarn_c90 (input_location, opt, "ISO C90 forbids variable "
> +                  "length array");
>      }
>  }
>  
> @@ -5186,18 +5157,14 @@ grokdeclarator (const struct c_declarator *declarator,
>    as2 = TYPE_ADDR_SPACE (element_type);
>    address_space = ADDR_SPACE_GENERIC_P (as1)? as2 : as1;
>  
> -  if (pedantic && !flag_isoc99)
> -    {
> -      if (constp > 1)
> -     pedwarn (loc, OPT_Wpedantic, "duplicate %<const%>");
> -      if (restrictp > 1)
> -     pedwarn (loc, OPT_Wpedantic, "duplicate %<restrict%>");
> -      if (volatilep > 1)
> -     pedwarn (loc, OPT_Wpedantic, "duplicate %<volatile%>");
> -      if (atomicp > 1)
> -     pedwarn (loc, OPT_Wpedantic, "duplicate %<_Atomic%>");
> -
> -    }
> +  if (constp > 1)
> +    pedwarn_c90 (loc, OPT_Wpedantic, "duplicate %<const%>");
> +  if (restrictp > 1)
> +    pedwarn_c90 (loc, OPT_Wpedantic, "duplicate %<restrict%>");
> +  if (volatilep > 1)
> +    pedwarn_c90 (loc, OPT_Wpedantic, "duplicate %<volatile%>");
> +  if (atomicp > 1)
> +    pedwarn_c90 (loc, OPT_Wpedantic, "duplicate %<_Atomic%>");
>  
>    if (!ADDR_SPACE_GENERIC_P (as1) && !ADDR_SPACE_GENERIC_P (as2) && as1 != 
> as2)
>      error_at (loc, "conflicting named address spaces (%s vs %s)",
> @@ -5602,10 +5569,9 @@ grokdeclarator (const struct c_declarator *declarator,
>                   flexible_array_member = (t->kind == cdk_id);
>                 }
>               if (flexible_array_member
> -                 && pedantic && !flag_isoc99
>                   && !in_system_header_at (input_location))
> -               pedwarn (loc, OPT_Wpedantic,
> -                        "ISO C90 does not support flexible array members");
> +               pedwarn_c90 (loc, OPT_Wpedantic, "ISO C90 does not "
> +                            "support flexible array members");
>  
>               /* ISO C99 Flexible array members are effectively
>                  identical to GCC's zero-length array extension.  */
> @@ -9140,8 +9106,8 @@ declspecs_add_qual (source_location loc,
>      default:
>        gcc_unreachable ();
>      }
> -  if (dupe && !flag_isoc99)
> -    pedwarn (loc, OPT_Wpedantic, "duplicate %qE", qual);
> +  if (dupe)
> +    pedwarn_c90 (loc, OPT_Wpedantic, "duplicate %qE", qual);
>    return specs;
>  }
>  
> @@ -9385,9 +9351,9 @@ declspecs_add_type (location_t loc, struct c_declspecs 
> *specs,
>             break;
>           case RID_COMPLEX:
>             dupe = specs->complex_p;
> -           if (!flag_isoc99 && !in_system_header_at (loc))
> -             pedwarn (loc, OPT_Wpedantic,
> -                      "ISO C90 does not support complex types");
> +           if (!in_system_header_at (loc))
> +             pedwarn_c90 (loc, OPT_Wpedantic,
> +                          "ISO C90 does not support complex types");
>             if (specs->typespec_word == cts_auto_type)
>               error_at (loc,
>                         ("both %<complex%> and %<__auto_type%> in "
> @@ -9603,9 +9569,9 @@ declspecs_add_type (location_t loc, struct c_declspecs 
> *specs,
>               }
>             return specs;
>           case RID_BOOL:
> -           if (!flag_isoc99 && !in_system_header_at (loc))
> -             pedwarn (loc, OPT_Wpedantic,
> -                      "ISO C90 does not support boolean types");
> +           if (!in_system_header_at (loc))
> +             pedwarn_c90 (loc, OPT_Wpedantic,
> +                          "ISO C90 does not support boolean types");
>             if (specs->long_p)
>               error_at (loc,
>                         ("both %<long%> and %<_Bool%> in "
> diff --git gcc/gcc/c/c-errors.c gcc/gcc/c/c-errors.c
> index 92136e7..1cc1dbf 100644
> --- gcc/gcc/c/c-errors.c
> +++ gcc/gcc/c/c-errors.c
> @@ -44,21 +44,38 @@ pedwarn_c99 (location_t location, int opt, const char 
> *gmsgid, ...)
>    va_end (ap);
>  }
>  
> -/* Issue an ISO C90 pedantic warning MSGID.  This function is supposed to
> -   be used for matters that are allowed in ISO C99 but not supported in
> -   ISO C90, thus we explicitly don't pedwarn when C99 is specified.
> -   (There is no flag_c90.)  */
> +/* Issue an ISO C90 pedantic warning MSGID if -pedantic outside C99 mode,
> +   otherwise issue warning MSGID if -Wc90-c99-compat is specified, or if
> +   specific option such as -Wlong-long is specified.
> +   This function is supposed to be used for matters that are allowed in
> +   ISO C99 but not supported in ISO C90, thus we explicitly don't pedwarn
> +   when C99 is specified.  (There is no flag_c90.)  */
>  
>  void
>  pedwarn_c90 (location_t location, int opt, const char *gmsgid, ...)
>  {
>    diagnostic_info diagnostic;
>    va_list ap;
> +  bool warned = false;
>  
>    va_start (ap, gmsgid);
> -  diagnostic_set_info (&diagnostic, gmsgid, &ap, location,
> -                    flag_isoc99 ? DK_WARNING : DK_PEDWARN);
> -  diagnostic.option_index = opt;
> -  report_diagnostic (&diagnostic);
> +  if (pedantic && !flag_isoc99)
> +    {
> +      diagnostic_set_info (&diagnostic, gmsgid, &ap, location, DK_PEDWARN);
> +      diagnostic.option_index = opt;
> +      warned = report_diagnostic (&diagnostic);
> +    }
> +  else if (opt != OPT_Wpedantic)
> +    {
> +      diagnostic_set_info (&diagnostic, gmsgid, &ap, location, DK_WARNING);
> +      diagnostic.option_index = opt;
> +      warned = report_diagnostic (&diagnostic);
> +    }
> +  if (warn_c90_c99_compat && !warned)
> +    {
> +      diagnostic_set_info (&diagnostic, gmsgid, &ap, location, DK_WARNING);
> +      diagnostic.option_index = OPT_Wc90_c99_compat;
> +      report_diagnostic (&diagnostic);
> +    }
>    va_end (ap);
>  }
> diff --git gcc/gcc/c/c-parser.c gcc/gcc/c/c-parser.c
> index e32bf04..ca8577c 100644
> --- gcc/gcc/c/c-parser.c
> +++ gcc/gcc/c/c-parser.c
> @@ -1072,7 +1072,8 @@ disable_extension_diagnostics (void)
>            | (flag_iso << 3)
>            | (warn_long_long << 4)
>            | (warn_cxx_compat << 5)
> -          | (warn_overlength_strings << 6));
> +          | (warn_overlength_strings << 6)
> +          | (warn_c90_c99_compat << 7));
>    cpp_opts->cpp_pedantic = pedantic = 0;
>    warn_pointer_arith = 0;
>    cpp_opts->cpp_warn_traditional = warn_traditional = 0;
> @@ -1080,6 +1081,7 @@ disable_extension_diagnostics (void)
>    cpp_opts->cpp_warn_long_long = warn_long_long = 0;
>    warn_cxx_compat = 0;
>    warn_overlength_strings = 0;
> +  warn_c90_c99_compat = 0;
>    return ret;
>  }
>  
> @@ -1096,6 +1098,7 @@ restore_extension_diagnostics (int flags)
>    cpp_opts->cpp_warn_long_long = warn_long_long = (flags >> 4) & 1;
>    warn_cxx_compat = (flags >> 5) & 1;
>    warn_overlength_strings = (flags >> 6) & 1;
> +  warn_c90_c99_compat = (flags >> 7) & 1;
>  }
>  
>  /* Possibly kinds of declarator to parse.  */
> @@ -2545,8 +2548,9 @@ c_parser_enum_specifier (c_parser *parser)
>           }
>         if (c_parser_next_token_is (parser, CPP_CLOSE_BRACE))
>           {
> -           if (seen_comma && !flag_isoc99)
> -             pedwarn (comma_loc, OPT_Wpedantic, "comma at end of enumerator 
> list");
> +           if (seen_comma)
> +             pedwarn_c90 (comma_loc, OPT_Wpedantic,
> +                          "comma at end of enumerator list");
>             c_parser_consume_token (parser);
>             break;
>           }
> @@ -4348,9 +4352,9 @@ c_parser_initelt (c_parser *parser, struct obstack * 
> braced_init_obstack)
>       {
>         if (c_parser_next_token_is (parser, CPP_EQ))
>           {
> -           if (!flag_isoc99)
> -             pedwarn (des_loc, OPT_Wpedantic,
> -                      "ISO C90 forbids specifying subobject to initialize");
> +           pedwarn_c90 (des_loc, OPT_Wpedantic,
> +                        "ISO C90 forbids specifying subobject "
> +                        "to initialize");
>             c_parser_consume_token (parser);
>           }
>         else
> @@ -4566,10 +4570,9 @@ c_parser_compound_statement_nostart (c_parser *parser)
>         c_parser_declaration_or_fndef (parser, true, true, true, true,
>                                        true, NULL, vNULL);
>         if (last_stmt)
> -         pedwarn_c90 (loc,
> -                      (pedantic && !flag_isoc99)
> -                      ? OPT_Wpedantic
> -                      : OPT_Wdeclaration_after_statement,
> +         pedwarn_c90 (loc, (pedantic && !flag_isoc99)
> +                            ? OPT_Wpedantic
> +                            : OPT_Wdeclaration_after_statement,
>                        "ISO C90 forbids mixed declarations and code");
>         last_stmt = false;
>       }
> @@ -4598,8 +4601,8 @@ c_parser_compound_statement_nostart (c_parser *parser)
>             restore_extension_diagnostics (ext);
>             if (last_stmt)
>               pedwarn_c90 (loc, (pedantic && !flag_isoc99)
> -                          ? OPT_Wpedantic
> -                          : OPT_Wdeclaration_after_statement,
> +                               ? OPT_Wpedantic
> +                               : OPT_Wdeclaration_after_statement,
>                            "ISO C90 forbids mixed declarations and code");
>             last_stmt = false;
>           }
> @@ -7401,9 +7404,8 @@ c_parser_postfix_expression (c_parser *parser)
>               expr.value = error_mark_node;
>               break;
>             }
> -         if (!flag_isoc99)
> -           pedwarn (loc, OPT_Wpedantic,
> -                    "ISO C90 does not support complex types");
> +         pedwarn_c90 (loc, OPT_Wpedantic,
> +                      "ISO C90 does not support complex types");
>           expr.value = build2 (COMPLEX_EXPR,
>                                build_complex_type
>                                  (TYPE_MAIN_VARIANT
> @@ -7607,8 +7609,7 @@ c_parser_postfix_expression_after_paren_type (c_parser 
> *parser,
>        type = error_mark_node;
>      }
>  
> -  if (!flag_isoc99)
> -    pedwarn (start_loc, OPT_Wpedantic, "ISO C90 forbids compound literals");
> +  pedwarn_c90 (start_loc, OPT_Wpedantic, "ISO C90 forbids compound 
> literals");
>    non_const = ((init.value && TREE_CODE (init.value) == CONSTRUCTOR)
>              ? CONSTRUCTOR_NON_CONST (init.value)
>              : init.original_code == C_MAYBE_CONST_EXPR);
> diff --git gcc/gcc/c/c-tree.h gcc/gcc/c/c-tree.h
> index f97d0d5..55e71dc 100644
> --- gcc/gcc/c/c-tree.h
> +++ gcc/gcc/c/c-tree.h
> @@ -676,7 +676,9 @@ extern tree c_omp_reduction_lookup (tree, tree);
>  extern tree c_check_omp_declare_reduction_r (tree *, int *, void *);
>  
>  /* In c-errors.c */
> -extern void pedwarn_c90 (location_t, int opt, const char *, ...) 
> ATTRIBUTE_GCC_DIAG(3,4);
> -extern void pedwarn_c99 (location_t, int opt, const char *, ...) 
> ATTRIBUTE_GCC_DIAG(3,4);
> +extern void pedwarn_c90 (location_t, int opt, const char *, ...)
> +    ATTRIBUTE_GCC_DIAG(3,4);
> +extern void pedwarn_c99 (location_t, int opt, const char *, ...)
> +    ATTRIBUTE_GCC_DIAG(3,4);
>  
>  #endif /* ! GCC_C_TREE_H */
> diff --git gcc/gcc/c/c-typeck.c gcc/gcc/c/c-typeck.c
> index a938933..64c7a74 100644
> --- gcc/gcc/c/c-typeck.c
> +++ gcc/gcc/c/c-typeck.c
> @@ -2511,7 +2511,7 @@ build_array_ref (location_t loc, tree array, tree index)
>           return error_mark_node;
>       }
>  
> -      if (pedantic)
> +      if (pedantic || warn_c90_c99_compat)
>       {
>         tree foo = array;
>         while (TREE_CODE (foo) == COMPONENT_REF)
> @@ -2519,9 +2519,10 @@ build_array_ref (location_t loc, tree array, tree 
> index)
>         if (TREE_CODE (foo) == VAR_DECL && C_DECL_REGISTER (foo))
>           pedwarn (loc, OPT_Wpedantic,
>                    "ISO C forbids subscripting %<register%> array");
> -       else if (!flag_isoc99 && !lvalue_p (foo))
> -         pedwarn (loc, OPT_Wpedantic,
> -                  "ISO C90 forbids subscripting non-lvalue array");
> +       else if (!lvalue_p (foo))
> +         pedwarn_c90 (loc, OPT_Wpedantic,
> +                      "ISO C90 forbids subscripting non-lvalue "
> +                      "array");
>       }
>  
>        type = TREE_TYPE (TREE_TYPE (array));
> diff --git gcc/gcc/doc/invoke.texi gcc/gcc/doc/invoke.texi
> index 51757f0..f48552b 100644
> --- gcc/gcc/doc/invoke.texi
> +++ gcc/gcc/doc/invoke.texi
> @@ -241,6 +241,7 @@ Objective-C and Objective-C++ Dialects}.
>  -w  -Wextra  -Wall  -Waddress  -Waggregate-return  @gol
>  -Waggressive-loop-optimizations -Warray-bounds @gol
>  -Wno-attributes -Wno-builtin-macro-redefined @gol
> +-Wc90-c99-compat @gol
>  -Wc++-compat -Wc++11-compat -Wcast-align  -Wcast-qual  @gol
>  -Wchar-subscripts -Wclobbered  -Wcomment -Wconditionally-supported  @gol
>  -Wconversion -Wcoverage-mismatch -Wdate-time -Wdelete-incomplete -Wno-cpp  
> @gol
> @@ -4497,6 +4498,15 @@ example, warn if an unsigned variable is compared 
> against zero with
>  Warn whenever a function call is cast to a non-matching type.
>  For example, warn if @code{int malloc()} is cast to @code{anything *}.
>  
> +@item -Wc90-c99-compat @r{(C and Objective-C only)}
> +@opindex Wc90-c99-compat
> +@opindex Wno-c90-c99-compat
> +Warn about features not present in ISO C90, but present in ISO C99.
> +For instance, warn about use of variable length arrays, @code{long long}
> +type, @code{bool} type, compound literals, designated initializers, and so
> +on.  This option is independent of the standards mode.  Warnings are disabled
> +in the expression that follows @code{__extension__}.
> +
>  @item -Wc++-compat @r{(C and Objective-C only)}
>  Warn about ISO C constructs that are outside of the common subset of
>  ISO C and ISO C++, e.g.@: request for implicit conversion from
> diff --git gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-1.c 
> gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-1.c
> index e69de29..15e71e8 100644
> --- gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-1.c
> +++ gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-1.c
> @@ -0,0 +1,56 @@
> +/* { dg-do compile } */
> +/* { dg-options "-std=gnu90 -Wpedantic -Wc90-c99-compat" } */
> +
> +_Bool b; /* { dg-warning "ISO C90 does not support boolean types" } */
> +_Complex double c = __builtin_complex (0.0, 0.0); /* { dg-warning "ISO C90 
> does not support complex types" } */
> +long long l; /* { dg-warning "ISO C90 does not support .long long." } */
> +struct A { int i; char a[]; }; /* { dg-warning "ISO C90 does not support 
> flexible array members" } */
> +struct { long int b: 2; } s; /* { dg-warning "type of bit-field .b. is a GCC 
> extension" } */
> +const const int i; /* { dg-warning "duplicate .const." } */
> +volatile volatile v; /* { dg-warning "duplicate .volatile." } */
> +
> +struct S { int a[2]; };
> +extern struct S foo (void);
> +
> +#define V(v, ...) (v, __VA_ARGS) /* { dg-warning "anonymous variadic macros 
> were introduced in C99" } */
> +
> +enum { E, }; /* { dg-warning "comma at end of enumerator list" } */
> +
> +void fn1 (char [*]); /* { dg-warning "ISO C90 does not support 
> .\\\[\\\*\\\]. array declarators" } */
> +
> +void
> +fn2 (char x[static 4]) /* { dg-warning "ISO C90 does not support .static. or 
> type qualifiers" } */
> +{
> +  int i = (int) { 1 }; /* { dg-warning "ISO C90 forbids compound literals" } 
> */
> +  struct A a = { .i = 3 }; /* { dg-warning "ISO C90 forbids specifying 
> subobject to initialize" } */
> +}
> +
> +void
> +fn3 (int n)
> +{
> +  n = 3;
> +  int i; /* { dg-warning "ISO C90 forbids mixed declarations and code" } */
> +}
> +
> +void
> +fn4 (int n)
> +{
> +  n = 3;
> +  __extension__ int i; /* { dg-warning "ISO C90 forbids mixed declarations 
> and code" } */
> +}
> +
> +void
> +fn5 (void)
> +{
> +  (foo ()).a[0]; /* { dg-warning "ISO C90 forbids subscripting non-lvalue 
> array" } */
> +}
> +
> +#define F(a) a
> +
> +void
> +fn6 (void)
> +{
> +  F(); /* { dg-warning "invoking macro F argument" } */
> +}
> +
> +void fn7 (int n, int a[n]); /* { dg-warning "ISO C90 forbids variable length 
> array .a." } */
> diff --git gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-2.c 
> gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-2.c
> index e69de29..d00f0df 100644
> --- gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-2.c
> +++ gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-2.c
> @@ -0,0 +1,56 @@
> +/* { dg-do compile } */
> +/* { dg-options "-std=gnu99 -Wc90-c99-compat -pedantic-errors" } */
> +
> +_Bool b; /* { dg-warning "ISO C90 does not support boolean types" } */
> +_Complex double c = __builtin_complex (0.0, 0.0); /* { dg-warning "ISO C90 
> does not support complex types" } */
> +long long l; /* { dg-warning "ISO C90 does not support .long long." } */
> +struct A { int i; char a[]; }; /* { dg-warning "ISO C90 does not support 
> flexible array members" } */
> +struct { long int b: 2; } s; /* { dg-warning "type of bit-field .b. is a GCC 
> extension" } */
> +const const int i; /* { dg-warning "duplicate .const." } */
> +volatile volatile int v; /* { dg-warning "duplicate .volatile." } */
> +
> +struct S { int a[2]; };
> +extern struct S foo (void);
> +
> +#define V(v, ...) (v, __VA_ARGS) /* { dg-warning "anonymous variadic macros 
> were introduced in C99" } */
> +
> +enum { E, }; /* { dg-warning "comma at end of enumerator list" } */
> +
> +void fn1 (char [*]); /* { dg-warning "ISO C90 does not support 
> .\\\[\\\*\\\]. array declarators" } */
> +
> +void
> +fn2 (char x[static 4]) /* { dg-warning "ISO C90 does not support .static. or 
> type qualifiers" } */
> +{
> +  int i = (int) { 1 }; /* { dg-warning "ISO C90 forbids compound literals" } 
> */
> +  struct A a = { .i = 3 }; /* { dg-warning "ISO C90 forbids specifying 
> subobject to initialize" } */
> +}
> +
> +void
> +fn3 (int n)
> +{
> +  n = 3;
> +  int i; /* { dg-warning "ISO C90 forbids mixed declarations and code" } */
> +}
> +
> +void
> +fn4 (int n)
> +{
> +  n = 3;
> +  __extension__ int i; /* { dg-warning "ISO C90 forbids mixed declarations 
> and code" } */
> +}
> +
> +void
> +fn5 (void)
> +{
> +  (foo ()).a[0]; /* { dg-warning "ISO C90 forbids subscripting non-lvalue 
> array" } */
> +}
> +
> +#define F(a) a
> +
> +void
> +fn6 (void)
> +{
> +  F(); /* { dg-warning "invoking macro F argument" } */
> +}
> +
> +void fn7 (int n, int a[n]); /* { dg-warning "ISO C90 forbids variable length 
> array .a." } */
> diff --git gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-3.c 
> gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-3.c
> index e69de29..78f012c 100644
> --- gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-3.c
> +++ gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-3.c
> @@ -0,0 +1,56 @@
> +/* { dg-do compile } */
> +/* { dg-options "-std=gnu11 -Wc90-c99-compat -pedantic-errors" } */
> +
> +_Bool b; /* { dg-warning "ISO C90 does not support boolean types" } */
> +_Complex double c = __builtin_complex (0.0, 0.0); /* { dg-warning "ISO C90 
> does not support complex types" } */
> +long long l; /* { dg-warning "ISO C90 does not support .long long." } */
> +struct A { int i; char a[]; }; /* { dg-warning "ISO C90 does not support 
> flexible array members" } */
> +struct { long int b: 2; } s; /* { dg-warning "type of bit-field .b. is a GCC 
> extension" } */
> +const const int i; /* { dg-warning "duplicate .const." } */
> +volatile volatile int v; /* { dg-warning "duplicate .volatile." } */
> +
> +struct S { int a[2]; };
> +extern struct S foo (void);
> +
> +#define V(v, ...) (v, __VA_ARGS) /* { dg-warning "anonymous variadic macros 
> were introduced in C99" } */
> +
> +enum { E, }; /* { dg-warning "comma at end of enumerator list" } */
> +
> +void fn1 (char [*]); /* { dg-warning "ISO C90 does not support 
> .\\\[\\\*\\\]. array declarators" } */
> +
> +void
> +fn2 (char x[static 4]) /* { dg-warning "ISO C90 does not support .static. or 
> type qualifiers" } */
> +{
> +  int i = (int) { 1 }; /* { dg-warning "ISO C90 forbids compound literals" } 
> */
> +  struct A a = { .i = 3 }; /* { dg-warning "ISO C90 forbids specifying 
> subobject to initialize" } */
> +}
> +
> +void
> +fn3 (int n)
> +{
> +  n = 3;
> +  int i; /* { dg-warning "ISO C90 forbids mixed declarations and code" } */
> +}
> +
> +void
> +fn4 (int n)
> +{
> +  n = 3;
> +  __extension__ int i; /* { dg-warning "ISO C90 forbids mixed declarations 
> and code" } */
> +}
> +
> +void
> +fn5 (void)
> +{
> +  (foo ()).a[0]; /* { dg-warning "ISO C90 forbids subscripting non-lvalue 
> array" } */
> +}
> +
> +#define F(a) a
> +
> +void
> +fn6 (void)
> +{
> +  F(); /* { dg-warning "invoking macro F argument" } */
> +}
> +
> +void fn7 (int n, int a[n]); /* { dg-warning "ISO C90 forbids variable length 
> array .a." } */
> diff --git gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-4.c 
> gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-4.c
> index e69de29..e8d2f03 100644
> --- gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-4.c
> +++ gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-4.c
> @@ -0,0 +1,56 @@
> +/* { dg-do compile } */
> +/* { dg-options "-std=gnu90 -Wpedantic -Wno-c90-c99-compat" } */
> +
> +_Bool b; /* { dg-warning "ISO C90 does not support boolean types" } */
> +_Complex double c = __builtin_complex (0.0, 0.0); /* { dg-warning "ISO C90 
> does not support complex types" } */
> +long long l; /* { dg-warning "ISO C90 does not support .long long." } */
> +struct A { int i; char a[]; }; /* { dg-warning "ISO C90 does not support 
> flexible array members" } */
> +struct { long int b: 2; } s; /* { dg-warning "type of bit-field .b. is a GCC 
> extension" } */
> +const const int i; /* { dg-warning "duplicate .const." } */
> +volatile volatile int v; /* { dg-warning "duplicate .volatile." } */
> +
> +struct S { int a[2]; };
> +extern struct S foo (void);
> +
> +#define V(v, ...) (v, __VA_ARGS) /* { dg-warning "anonymous variadic macros 
> were introduced in C99" } */
> +
> +enum { E, }; /* { dg-warning "comma at end of enumerator list" } */
> +
> +void fn1 (char [*]); /* { dg-warning "ISO C90 does not support 
> .\\\[\\\*\\\]. array declarators" } */
> +
> +void
> +fn2 (char x[static 4]) /* { dg-warning "ISO C90 does not support .static. or 
> type qualifiers" } */
> +{
> +  int i = (int) { 1 }; /* { dg-warning "ISO C90 forbids compound literals" } 
> */
> +  struct A a = { .i = 3 }; /* { dg-warning "ISO C90 forbids specifying 
> subobject to initialize" } */
> +}
> +
> +void
> +fn3 (int n)
> +{
> +  n = 3;
> +  int i; /* { dg-warning "ISO C90 forbids mixed declarations and code" } */
> +}
> +
> +void
> +fn4 (int n)
> +{
> +  n = 3;
> +  __extension__ int i; /* { dg-warning "ISO C90 forbids mixed declarations 
> and code" } */
> +}
> +
> +void
> +fn5 (void)
> +{
> +  (foo ()).a[0]; /* { dg-warning "ISO C90 forbids subscripting non-lvalue 
> array" } */
> +}
> +
> +#define F(a) a
> +
> +void
> +fn6 (void)
> +{
> +  F(); /* { dg-warning "invoking macro F argument" } */
> +}
> +
> +void fn7 (int n, int a[n]); /* { dg-warning "ISO C90 forbids variable length 
> array .a." } */
> diff --git gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-5.c 
> gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-5.c
> index e69de29..1344ae8 100644
> --- gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-5.c
> +++ gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-5.c
> @@ -0,0 +1,56 @@
> +/* { dg-do compile } */
> +/* { dg-options "-std=gnu90 -pedantic-errors -Wno-c90-c99-compat" } */
> +
> +_Bool b; /* { dg-error "ISO C90 does not support boolean types" } */
> +_Complex double c = __builtin_complex (0.0, 0.0); /* { dg-error "ISO C90 
> does not support complex types" } */
> +long long l; /* { dg-error "ISO C90 does not support .long long." } */
> +struct A { int i; char a[]; }; /* { dg-error "ISO C90 does not support 
> flexible array members" } */
> +struct { long int b: 2; } s; /* { dg-error "type of bit-field .b. is a GCC 
> extension" } */
> +const const int i; /* { dg-error "duplicate .const." } */
> +volatile volatile int v; /* { dg-error "duplicate .volatile." } */
> +
> +struct S { int a[2]; };
> +extern struct S foo (void);
> +
> +#define V(v, ...) (v, __VA_ARGS) /* { dg-error "anonymous variadic macros 
> were introduced in C99" } */
> +
> +enum { E, }; /* { dg-error "comma at end of enumerator list" } */
> +
> +void fn1 (char [*]); /* { dg-error "ISO C90 does not support .\\\[\\\*\\\]. 
> array declarators" } */
> +
> +void
> +fn2 (char x[static 4]) /* { dg-error "ISO C90 does not support .static. or 
> type qualifiers" } */
> +{
> +  int i = (int) { 1 }; /* { dg-error "ISO C90 forbids compound literals" } */
> +  struct A a = { .i = 3 }; /* { dg-error "ISO C90 forbids specifying 
> subobject to initialize" } */
> +}
> +
> +void
> +fn3 (int n)
> +{
> +  n = 3;
> +  int i; /* { dg-error "ISO C90 forbids mixed declarations and code" } */
> +}
> +
> +void
> +fn4 (int n)
> +{
> +  n = 3;
> +  __extension__ int i; /* { dg-error "ISO C90 forbids mixed declarations and 
> code" } */
> +}
> +
> +void
> +fn5 (void)
> +{
> +  (foo ()).a[0]; /* { dg-error "ISO C90 forbids subscripting non-lvalue 
> array" } */
> +}
> +
> +#define F(a) a
> +
> +void
> +fn6 (void)
> +{
> +  F(); /* { dg-error "invoking macro F argument" } */
> +}
> +
> +void fn7 (int n, int a[n]); /* { dg-error "ISO C90 forbids variable length 
> array .a." } */
> diff --git gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-6.c 
> gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-6.c
> index e69de29..8728cd9 100644
> --- gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-6.c
> +++ gcc/gcc/testsuite/gcc.dg/Wc90-c99-compat-6.c
> @@ -0,0 +1,29 @@
> +/* { dg-do compile } */
> +/* { dg-options "-std=gnu90 -Wc90-c99-compat" } */
> +
> +__extension__ _Bool b;
> +__extension__ _Complex double c = __builtin_complex (0.0, 0.0);
> +__extension__ long long l;
> +__extension__ struct A { int i; char a[]; };
> +__extension__ struct { long int b: 2; } s;
> +__extension__ const const int i;
> +__extension__ volatile volatile int v;
> +__extension__ struct S { int a[2]; };
> +extern struct S foo (void);
> +__extension__ enum { E, };
> +__extension__ void fn1 (char [*]);
> +
> +__extension__ void
> +fn2 (char x[static 4])
> +{
> +  int i = (int) { 1 };
> +  struct A a = { .i = 3 };
> +}
> +
> +__extension__ void
> +fn5 (void)
> +{
> +  (foo ()).a[0];
> +}
> +
> +__extension__ void fn7 (int n, int a[n]);
> diff --git gcc/gcc/testsuite/gcc.dg/wvla-1.c gcc/gcc/testsuite/gcc.dg/wvla-1.c
> index c8f2107..d2e3cb5 100644
> --- gcc/gcc/testsuite/gcc.dg/wvla-1.c
> +++ gcc/gcc/testsuite/gcc.dg/wvla-1.c
> @@ -2,4 +2,4 @@
>  /* { dg-options "-std=c89 -Wvla" } */
>  
>  extern void 
> -func (int i, int array[i]); /* { dg-warning "variable length array 'array' 
> is used" } */
> +func (int i, int array[i]); /* { dg-warning "ISO C90 forbids variable length 
> array 'array'" } */
> diff --git gcc/gcc/testsuite/gcc.dg/wvla-2.c gcc/gcc/testsuite/gcc.dg/wvla-2.c
> index d811a11..92c67ed 100644
> --- gcc/gcc/testsuite/gcc.dg/wvla-2.c
> +++ gcc/gcc/testsuite/gcc.dg/wvla-2.c
> @@ -2,4 +2,4 @@
>  /* { dg-options "-std=c99 -Wvla" } */
>  
>  extern void 
> -func (int i, int array[i]); /* { dg-warning "variable length array 'array' 
> is used" } */
> +func (int i, int array[i]); /* { dg-warning "ISO C90 forbids variable length 
> array 'array'" } */
> diff --git gcc/gcc/testsuite/gcc.dg/wvla-4.c gcc/gcc/testsuite/gcc.dg/wvla-4.c
> index 8c15292..ae2e0b0 100644
> --- gcc/gcc/testsuite/gcc.dg/wvla-4.c
> +++ gcc/gcc/testsuite/gcc.dg/wvla-4.c
> @@ -2,4 +2,4 @@
>  /* { dg-options "-pedantic-errors -std=c99 -Wvla" } */
>  
>  extern void 
> -func (int i, int array[i]); /* { dg-warning "variable length array 'array' 
> is used" } */
> +func (int i, int array[i]); /* { dg-warning "ISO C90 forbids variable length 
> array 'array'" } */
> diff --git gcc/gcc/testsuite/gcc.dg/wvla-6.c gcc/gcc/testsuite/gcc.dg/wvla-6.c
> index f21435b..694a4cc 100644
> --- gcc/gcc/testsuite/gcc.dg/wvla-6.c
> +++ gcc/gcc/testsuite/gcc.dg/wvla-6.c
> @@ -2,4 +2,4 @@
>  /* { dg-options "-std=c89 -Wvla" } */
>  
>  extern void 
> -func (int i, int [i]); /* { dg-warning "variable length array is used" } */
> +func (int i, int [i]); /* { dg-warning "ISO C90 forbids variable length 
> array" } */
> diff --git gcc/libcpp/charset.c gcc/libcpp/charset.c
> index a3c24d6..fa46f92 100644
> --- gcc/libcpp/charset.c
> +++ gcc/libcpp/charset.c
> @@ -995,6 +995,10 @@ _cpp_valid_ucn (cpp_reader *pfile, const uchar **pstr,
>    if (!CPP_OPTION (pfile, cplusplus) && !CPP_OPTION (pfile, c99))
>      cpp_error (pfile, CPP_DL_WARNING,
>              "universal character names are only valid in C++ and C99");
> +  else if (CPP_OPTION (pfile, cpp_warn_c90_c99_compat)
> +        && !CPP_OPTION (pfile, cplusplus))
> +    cpp_error (pfile, CPP_DL_WARNING,
> +            "C99's universal character names are incompatible with C90");
>    else if (CPP_WTRADITIONAL (pfile) && identifier_pos == 0)
>      cpp_warning (pfile, CPP_W_TRADITIONAL,
>                "the meaning of '\\%c' is different in traditional C",
> diff --git gcc/libcpp/include/cpplib.h gcc/libcpp/include/cpplib.h
> index a83452b..4cd66cd 100644
> --- gcc/libcpp/include/cpplib.h
> +++ gcc/libcpp/include/cpplib.h
> @@ -466,6 +466,9 @@ struct cpp_options
>    /* True if dependencies should be restored from a precompiled header.  */
>    bool restore_pch_deps;
>  
> +  /* True if warn about differences between C90 and C99.  */
> +  bool cpp_warn_c90_c99_compat;
> +
>    /* Dependency generation.  */
>    struct
>    {
> diff --git gcc/libcpp/lex.c gcc/libcpp/lex.c
> index 7e2db64..5cc2224 100644
> --- gcc/libcpp/lex.c
> +++ gcc/libcpp/lex.c
> @@ -2325,7 +2325,7 @@ _cpp_lex_direct (cpp_reader *pfile)
>        else if (c == '/' && (CPP_OPTION (pfile, cplusplus_comments)
>                           || cpp_in_system_header (pfile)))
>       {
> -       /* Warn about comments only if pedantically GNUC89, and not
> +       /* Warn about comments if pedantically GNUC89, and not
>            in system headers.  */
>         if (CPP_OPTION (pfile, lang) == CLK_GNUC89 && CPP_PEDANTIC (pfile)
>             && ! buffer->warned_cplusplus_comments)
> @@ -2336,6 +2336,16 @@ _cpp_lex_direct (cpp_reader *pfile)
>                        "(this will be reported only once per input file)");
>             buffer->warned_cplusplus_comments = 1;
>           }
> +       /* Or if specifically desired via -Wc90-c99-compat.  */
> +       else if (CPP_OPTION (pfile, cpp_warn_c90_c99_compat)
> +                && ! buffer->warned_cplusplus_comments)
> +         {
> +           cpp_error (pfile, CPP_DL_WARNING,
> +                      "C++ style comments are are incompatible with C90");
> +           cpp_error (pfile, CPP_DL_WARNING,
> +                      "(this will be reported only once per input file)");
> +           buffer->warned_cplusplus_comments = 1;
> +         }
>  
>         if (skip_line_comment (pfile) && CPP_OPTION (pfile, warn_comments))
>           cpp_warning (pfile, CPP_W_COMMENTS, "multi-line comment");
> diff --git gcc/libcpp/macro.c gcc/libcpp/macro.c
> index 556628b..ff6685c 100644
> --- gcc/libcpp/macro.c
> +++ gcc/libcpp/macro.c
> @@ -1795,6 +1795,16 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, 
> cpp_macro *macro,
>                      NODE_NAME (node),
>                      src->val.macro_arg.arg_no);
>       }
> +      else if (CPP_OPTION (pfile, cpp_warn_c90_c99_compat)
> +            && ! macro->syshdr
> +            && ! cpp_in_system_header (pfile)
> +            && ! CPP_OPTION (pfile, cplusplus))
> +     cpp_error (pfile, CPP_DL_WARNING,
> +                "invoking macro %s argument %d: "
> +                "empty macro arguments are undefined"
> +                " in ISO C90",
> +                NODE_NAME (node),
> +                src->val.macro_arg.arg_no);
>  
>        /* Avoid paste on RHS (even case count == 0).  */
>        if (!pfile->state.in_directive && !(src->flags & PASTE_LEFT))
> @@ -2848,6 +2858,10 @@ parse_params (cpp_reader *pfile, cpp_macro *macro)
>                       (pfile, CPP_W_VARIADIC_MACROS,
>                       "anonymous variadic macros were introduced in C99");
>               }
> +           else if (CPP_OPTION (pfile, cpp_warn_c90_c99_compat)
> +                    && ! CPP_OPTION (pfile, cplusplus))
> +             cpp_error (pfile, CPP_DL_WARNING,
> +                        "anonymous variadic macros were introduced in C99");
>           }
>         else if (CPP_OPTION (pfile, cpp_pedantic)
>                  && CPP_OPTION (pfile, warn_variadic_macros))
> 
>       Marek

        Marek

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