On Fri, Aug 17, 2018 at 12:16:07AM -0700, Omar Sandoval wrote: > On Thu, Aug 16, 2018 at 11:54:53PM -0700, Omar Sandoval wrote: > > On Thu, Aug 16, 2018 at 10:27:48PM -0700, Andrew Pinski wrote: > > > On Thu, Aug 16, 2018 at 9:29 PM Omar Sandoval <osan...@osandov.com> wrote: > > > > > > > > Hi, > > > > > > > > This fixes the issue that it is impossible to distinguish a zero-length > > > > array > > > > type from a flexible array type given the DWARF produced by GCC (which I > > > > reported here [1]). We do so by adding a DW_AT_count attribute with a > > > > value of > > > > zero only for zero-length arrays (this is what clang does in this case, > > > > too). > > > > > > > > 1: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86985 > > > > > > > > The reproducer from the PR now produces the expected output: > > > > > > > > $ ~/gcc-build/gcc/xgcc -B ~/gcc-build/gcc -g -c zero_length.c > > > > $ ~/gcc-build/gcc/xgcc -B ~/gcc-build/gcc -g -c flexible.c > > > > $ gdb -batch -ex 'ptype baz' zero_length.o > > > > type = struct { > > > > int foo; > > > > int bar[0]; > > > > } > > > > $ gdb -batch -ex 'ptype baz' flexible.o > > > > type = struct { > > > > int foo; > > > > int bar[]; > > > > } > > > > > > > > This was bootstrapped and tested on x86_64-pc-linux-gnu. > > > > > > > > I don't have commit rights (first time contributor), so if this change > > > > is okay > > > > could it please be applied? > > [snip] > > Here's the patch with the is_c () helper instead. > > 2018-08-17 Omar Sandoval <osan...@osandov.com> > > * dwarf2out.c (is_c): New. > (add_subscript_info): Add DW_AT_count of 0 for C zero-length arrays. > > diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c > index 5a74131d332..189f9bb381f 100644 > --- a/gcc/dwarf2out.c > +++ b/gcc/dwarf2out.c > @@ -3671,6 +3671,7 @@ static const char *get_AT_string (dw_die_ref, enum > dwarf_attribute); > static int get_AT_flag (dw_die_ref, enum dwarf_attribute); > static unsigned get_AT_unsigned (dw_die_ref, enum dwarf_attribute); > static inline dw_die_ref get_AT_ref (dw_die_ref, enum dwarf_attribute); > +static bool is_c (void); > static bool is_cxx (void); > static bool is_cxx (const_tree); > static bool is_fortran (void); > @@ -5434,6 +5435,19 @@ get_AT_file (dw_die_ref die, enum dwarf_attribute > attr_kind) > return a ? AT_file (a) : NULL; > } > > +/* Return TRUE if the language is C. */ > + > +static inline bool > +is_c (void) > +{ > + unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language); > + > + return (lang == DW_LANG_C || lang == DW_LANG_C89 || lang == DW_LANG_C99 > + || lang == DW_LANG_C11 || lang == DW_LANG_ObjC); > + > + > +} > + > /* Return TRUE if the language is C++. */ > > static inline bool > @@ -20918,12 +20932,24 @@ add_subscript_info (dw_die_ref type_die, tree type, > bool collapse_p) > dimension arr(N:*) > Since the debugger is definitely going to need to know N > to produce useful results, go ahead and output the lower > - bound solo, and hope the debugger can cope. */ > + bound solo, and hope the debugger can cope. > + > + For C and C++, if upper is NULL, this may be a zero-length array > + or a flexible array; we'd like to be able to distinguish between > + the two. Set DW_AT_count to 0 for the former. TYPE_SIZE is NULL > + for the latter. */ > > if (!get_AT (subrange_die, DW_AT_lower_bound)) > add_bound_info (subrange_die, DW_AT_lower_bound, lower, NULL); > - if (upper && !get_AT (subrange_die, DW_AT_upper_bound)) > - add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL); > + if (!get_AT (subrange_die, DW_AT_upper_bound) > + && !get_AT (subrange_die, DW_AT_count)) > + { > + if (upper) > + add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL); > + else if ((is_c () || is_cxx ()) && TYPE_SIZE (type)) > + add_bound_info (subrange_die, DW_AT_count, > + build_int_cst (TREE_TYPE (lower), 0), NULL); > + } > } > > /* Otherwise we have an array type with an unspecified length. The
Ping. Does this version look okay for trunk?
