> On Feb 25, 2022, at 6:43 AM, Richard Biener <rguent...@suse.de> wrote:
>
> On Thu, 24 Feb 2022, Qing Zhao wrote:
>
>>
>>
>>> On Feb 24, 2022, at 4:16 AM, Richard Biener <rguent...@suse.de> wrote:
>>>
>>> On Sat, 19 Feb 2022, Qing Zhao wrote:
>>>
>>>> Hi,
>>>>
>>>> This is the 2nd patch for fixing pr102276.
>>>>
>>>> Adding -Wtrivial-auto-var-init and update documentation.
>>>>
>>>> Adding a new warning option -Wtrivial-auto-var-init to report cases when
>>>> -ftrivial-auto-var-init cannot initialize the auto variable. At the same
>>>> time, update documentation for -ftrivial-auto-var-init to connect it with
>>>> the new warning option -Wtrivial-auto-var-init, and add documentation
>>>> for -Wtrivial-auto-var-init.
>>>>
>>>> Bootstraped and regression tested on both x86 and aarch64.
>>>>
>>>> Okay for committing?
>>>>
>>>> thanks.
>>>>
>>>> Qing.
>>>>
>>>> ==============================
>>>> From 4346890b8f4258489c4841f1992ba3ce816d7689 Mon Sep 17 00:00:00 2001
>>>> From: Qing Zhao <qing.z...@oracle.com>
>>>> Date: Fri, 18 Feb 2022 15:53:15 +0000
>>>> Subject: [PATCH 2/2] Adding -Wtrivial-auto-var-init and update
>>>> documentation.
>>>>
>>>> Adding a new warning option -Wtrivial-auto-var-init to report cases when
>>>> -ftrivial-auto-var-init cannot initialize the auto variable. At the same
>>>> time, update documentation for -ftrivial-auto-var-init to connect it with
>>>> the new warning option -Wtrivial-auto-var-init, and add documentation
>>>> for -Wtrivial-auto-var-init.
>>>>
>>>> 2022-02-18 Qing Zhao <qing.z...@oracle.com>
>>>> gcc/ChangeLog:
>>>>
>>>> * common.opt (-Wtrivial-auto-var-init): New option.
>>>> * doc/invoke.texi (-Wtrivial-auto-var-init): Document new option.
>>>> (-ftrivial-auto-var-init): Update option;
>>>> * gimplify.cc (maybe_warn_switch_unreachable): Rename...
>>>> (maybe_warn_switch_unreachable_and_auto_init): ...to this.
>>>> (gimplify_switch_expr): Call new function.
>>>>
>>>> gcc/testsuite/ChangeLog:
>>>>
>>>> * gcc.dg/auto-init-pr102276-3.c: New test.
>>>> * gcc.dg/auto-init-pr102276-4.c: New test.
>>>> ---
>>>> gcc/common.opt | 4 +
>>>> gcc/doc/invoke.texi | 14 ++-
>>>> gcc/gimplify.cc | 100 +++++++++++++++-----
>>>> gcc/testsuite/gcc.dg/auto-init-pr102276-3.c | 40 ++++++++
>>>> gcc/testsuite/gcc.dg/auto-init-pr102276-4.c | 40 ++++++++
>>>> 5 files changed, 175 insertions(+), 23 deletions(-)
>>>> create mode 100644 gcc/testsuite/gcc.dg/auto-init-pr102276-3.c
>>>> create mode 100644 gcc/testsuite/gcc.dg/auto-init-pr102276-4.c
>>>>
>>>> diff --git a/gcc/common.opt b/gcc/common.opt
>>>> index c21e5273ae3..22c95dbfa49 100644
>>>> --- a/gcc/common.opt
>>>> +++ b/gcc/common.opt
>>>> @@ -801,6 +801,10 @@ Wtrampolines
>>>> Common Var(warn_trampolines) Warning
>>>> Warn whenever a trampoline is generated.
>>>>
>>>> +Wtrivial-auto-var-init
>>>> +Common Var(warn_trivial_auto_var_init) Warning Init(0)
>>>> +Warn about where -ftrivial-auto-var-init cannot initialize the auto
>>>> variable.
>>>> +
>>>
>>> Warn about cases where ... initialize a variable.
>>
>> Okay.
>>
>>>
>>>> Wtype-limits
>>>> Common Var(warn_type_limits) Warning EnabledBy(Wextra)
>>>> Warn if a comparison is always true or always false due to the limited
>>>> range of the data type.
>>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>>> index e1a00c80307..c61a5b4b4a5 100644
>>>> --- a/gcc/doc/invoke.texi
>>>> +++ b/gcc/doc/invoke.texi
>>>> @@ -399,7 +399,7 @@ Objective-C and Objective-C++ Dialects}.
>>>> -Wswitch -Wno-switch-bool -Wswitch-default -Wswitch-enum @gol
>>>> -Wno-switch-outside-range -Wno-switch-unreachable -Wsync-nand @gol
>>>> -Wsystem-headers -Wtautological-compare -Wtrampolines -Wtrigraphs @gol
>>>> --Wtsan -Wtype-limits -Wundef @gol
>>>> +-Wtrivial-auto-var-init -Wtsan -Wtype-limits -Wundef @gol
>>>> -Wuninitialized -Wunknown-pragmas @gol
>>>> -Wunsuffixed-float-constants -Wunused @gol
>>>> -Wunused-but-set-parameter -Wunused-but-set-variable @gol
>>>> @@ -6953,6 +6953,14 @@ This warning is enabled by default for C and C++
>>>> programs.
>>>> Warn when @code{__sync_fetch_and_nand} and @code{__sync_nand_and_fetch}
>>>> built-in functions are used. These functions changed semantics in GCC 4.4.
>>>>
>>>> +@item -Wtrivial-auto-var-init
>>>> +@opindex Wtrivial-auto-var-init
>>>> +@opindex Wno-trivial-auto-var-init
>>>> +Warn when @code{-ftrivial-auto-var-init} cannot initialize the automatic
>>>> +variable. A common situation is an automatic variable that is declared
>>>> +between the controlling expression and the first case lable of a
>>>> @code{switch}
>>>> +statement.
>>>> +
>>>> @item -Wunused-but-set-parameter
>>>> @opindex Wunused-but-set-parameter
>>>> @opindex Wno-unused-but-set-parameter
>>>> @@ -12314,6 +12322,10 @@ initializer as uninitialized,
>>>> @option{-Wuninitialized} and
>>>> warning messages on such automatic variables.
>>>> With this option, GCC will also initialize any padding of automatic
>>>> variables
>>>> that have structure or union types to zeroes.
>>>> +However, the current implementation cannot initialize automatic variables
>>>> that
>>>> +are declared between the controlling expression and the first case of a
>>>> +@code{switch} statement. Using @option{-Wtrivial-auto-var-init} to
>>>> report all
>>>> +such cases.
>>>>
>>>> The three values of @var{choice} are:
>>>>
>>>> diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
>>>> index 4e3bbf5314d..7e52794691f 100644
>>>> --- a/gcc/gimplify.cc
>>>> +++ b/gcc/gimplify.cc
>>>> @@ -2079,13 +2079,59 @@ warn_switch_unreachable_r (gimple_stmt_iterator
>>>> *gsi_p, bool *handled_ops_p,
>>>> return NULL_TREE;
>>>> }
>>>>
>>>> +/* Callback for walk_gimple_seq. */
>>>> +
>>>> +static tree
>>>> +warn_switch_unreachable_auto_init_r (gimple_stmt_iterator *gsi_p,
>>>> + bool *handled_ops_p,
>>>> + struct walk_stmt_info *)
>>>> +{
>>>> + gimple *stmt = gsi_stmt (*gsi_p);
>>>> +
>>>> + *handled_ops_p = true;
>>>> + switch (gimple_code (stmt))
>>>> + {
>>>> + case GIMPLE_TRY:
>>>> + case GIMPLE_BIND:
>>>> + case GIMPLE_CATCH:
>>>> + case GIMPLE_EH_FILTER:
>>>> + case GIMPLE_TRANSACTION:
>>>> + /* Walk the sub-statements. */
>>>> + *handled_ops_p = false;
>>>> + break;
>>>> + case GIMPLE_CALL:
>>>> + if (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT)
>>>> + && flag_auto_var_init > AUTO_INIT_UNINITIALIZED)
>>>> + {
>>>> + /* Get the variable name from the 3rd argument of call. */
>>>> + tree var_name = gimple_call_arg (stmt, 2);
>>>> + var_name = TREE_OPERAND (TREE_OPERAND (var_name, 0), 0);
>>>> + const char *var_name_str = TREE_STRING_POINTER (var_name);
>>>> +
>>>> + warning_at (gimple_location (stmt), OPT_Wtrivial_auto_var_init,
>>>> + "%qs cannot be initialized with"
>>>> + "%<-ftrivial-auto-var_init%>",
>>>> + var_name_str);
>>>> + }
>>>> + break;
>>>> + case GIMPLE_LABEL:
>>>> + /* Stop till the first Label. */
>>>> + return integer_zero_node;
>>>> + default:
>>>> + break;
>>>> + }
>>>> + return NULL_TREE;
>>>> +}
>>>> +
>>>> /* Possibly warn about unreachable statements between switch's controlling
>>>> - expression and the first case. SEQ is the body of a switch
>>>> expression. */
>>>> + expression and the first case. Also warn about -ftrivial-auto-var-init
>>>> + cannot initialize the auto variable under such situation.
>>>> + SEQ is the body of a switch expression. */
>>>>
>>>> static void
>>>> -maybe_warn_switch_unreachable (gimple_seq seq)
>>>> +maybe_warn_switch_unreachable_and_auto_init (gimple_seq seq)
>>>> {
>>>> - if (!warn_switch_unreachable
>>>> + if ((!warn_switch_unreachable && !warn_trivial_auto_var_init)
>>>> /* This warning doesn't play well with Fortran when optimizations
>>>> are on. */
>>>> || lang_GNU_Fortran ()
>>>> @@ -2093,26 +2139,36 @@ maybe_warn_switch_unreachable (gimple_seq seq)
>>>> return;
>>>>
>>>> struct walk_stmt_info wi;
>>>> - memset (&wi, 0, sizeof (wi));
>>>> - walk_gimple_seq (seq, warn_switch_unreachable_r, NULL, &wi);
>>>> - gimple *stmt = (gimple *) wi.info;
>>>>
>>>> - if (stmt && gimple_code (stmt) != GIMPLE_LABEL)
>>>> + if (warn_switch_unreachable)
>>>> {
>>>> - if (gimple_code (stmt) == GIMPLE_GOTO
>>>> - && TREE_CODE (gimple_goto_dest (stmt)) == LABEL_DECL
>>>> - && DECL_ARTIFICIAL (gimple_goto_dest (stmt)))
>>>> - /* Don't warn for compiler-generated gotos. These occur
>>>> - in Duff's devices, for example. */
>>>> - ;
>>>> - else if ((flag_auto_var_init > AUTO_INIT_UNINITIALIZED)
>>>> - && (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT)))
>>>> - /* Don't warn for compiler-generated initializations for
>>>> - -ftrivial-auto-var-init. */
>>>> - ;
>>>> - else
>>>> - warning_at (gimple_location (stmt), OPT_Wswitch_unreachable,
>>>> - "statement will never be executed");
>>>> + memset (&wi, 0, sizeof (wi));
>>>> + walk_gimple_seq (seq, warn_switch_unreachable_r, NULL, &wi);
>>>> + gimple *stmt = (gimple *) wi.info;
>>>> +
>>>> + if (stmt && gimple_code (stmt) != GIMPLE_LABEL)
>>>> + {
>>>> + if (gimple_code (stmt) == GIMPLE_GOTO
>>>> + && TREE_CODE (gimple_goto_dest (stmt)) == LABEL_DECL
>>>> + && DECL_ARTIFICIAL (gimple_goto_dest (stmt)))
>>>> + /* Don't warn for compiler-generated gotos. These occur
>>>> + in Duff's devices, for example. */
>>>> + ;
>>>> + else if ((flag_auto_var_init > AUTO_INIT_UNINITIALIZED)
>>>> + && (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT)))
>>>> + /* Don't warn for compiler-generated initializations for
>>>> + -ftrivial-auto-var-init. */
>>>> + ;
>>>> + else
>>>> + warning_at (gimple_location (stmt), OPT_Wswitch_unreachable,
>>>> + "statement will never be executed");
>>>> + }
>>>> + }
>>>
>>> Hmm. I'd re-organize the code to emit both the Wswitch-unreachable
>>> and -Wtrivial_auto_var_init diagnostic from the existing
>>> warn_switch_unreachable_r callback. You can use wi.info to keep
>>> track whether a Wswitch-unreachable diagnostic was already emitted
>>> (and if -Wtrivial_auto_var_init is not enabled abort the walk)
>>> for example.
>>
>> Okay. Will try this.
>>
>> A question here: for the current -Wswitch-unreachable, the warning will be
>> emit only once for the first unreachable stmt.
>> Shall we emit warning for each unreachable stmt instead?
>
> No, only for the first one. But we might want to diagnose all
> not auto-init variables.
Okay.
Qing
>
> Richard.
>
>> thanks.
>>
>> Qing
>>>
>>> Thanks,
>>> Richard.
>>>
>>>> + if (warn_trivial_auto_var_init)
>>>> + {
>>>> + memset (&wi, 0, sizeof (wi));
>>>> + walk_gimple_seq (seq, warn_switch_unreachable_auto_init_r, NULL,
>>>> &wi);
>>>> }
>>>> }
>>>>
>>>> @@ -2646,7 +2702,7 @@ gimplify_switch_expr (tree *expr_p, gimple_seq
>>>> *pre_p)
>>>> gimplify_stmt (&SWITCH_BODY (switch_expr), &switch_body_seq);
>>>>
>>>> gimplify_ctxp->in_switch_expr = old_in_switch_expr;
>>>> - maybe_warn_switch_unreachable (switch_body_seq);
>>>> + maybe_warn_switch_unreachable_and_auto_init (switch_body_seq);
>>>> maybe_warn_implicit_fallthrough (switch_body_seq);
>>>> /* Only do this for the outermost GIMPLE_SWITCH. */
>>>> if (!gimplify_ctxp->in_switch_expr)
>>>> diff --git a/gcc/testsuite/gcc.dg/auto-init-pr102276-3.c
>>>> b/gcc/testsuite/gcc.dg/auto-init-pr102276-3.c
>>>> new file mode 100644
>>>> index 00000000000..f113f46e29d
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/auto-init-pr102276-3.c
>>>> @@ -0,0 +1,40 @@
>>>> +/* { dg-do compile } */
>>>> +/* { dg-options "-O2 -Wtrivial-auto-var-init
>>>> -ftrivial-auto-var-init=zero" } */
>>>> +
>>>> +int g(int *, int *);
>>>> +int f()
>>>> +{
>>>> + switch (0) {
>>>> + int x; /* { dg-warning "cannot be initialized with" } */
>>>> + int y; /* { dg-warning "cannot be initialized with" } */
>>>> + default:
>>>> + return g(&x, &y);
>>>> + }
>>>> +}
>>>> +
>>>> +int g1(int, int);
>>>> +int f1()
>>>> +{
>>>> + switch (0) {
>>>> + int x; /* { dg-warning "cannot be initialized with" } */
>>>> + int y; /* { dg-warning "cannot be initialized with" } */
>>>> + default:
>>>> + return g1(x, y);
>>>> + }
>>>> +}
>>>> +
>>>> +struct S
>>>> +{
>>>> + char a;
>>>> + int b;
>>>> +};
>>>> +int g2(int);
>>>> +int f2(int input)
>>>> +{
>>>> + switch (0) {
>>>> + struct S x; /* { dg-warning "cannot be initialized with" } */
>>>> + struct S y; /* { dg-warning "cannot be initialized with" } */
>>>> + default:
>>>> + return g2(input) + x.b + y.b;
>>>> + }
>>>> +}
>>>> diff --git a/gcc/testsuite/gcc.dg/auto-init-pr102276-4.c
>>>> b/gcc/testsuite/gcc.dg/auto-init-pr102276-4.c
>>>> new file mode 100644
>>>> index 00000000000..662e0d1182e
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/auto-init-pr102276-4.c
>>>> @@ -0,0 +1,40 @@
>>>> +/* { dg-do compile } */
>>>> +/* { dg-options "-O2 -Wtrivial-auto-var-init
>>>> -ftrivial-auto-var-init=pattern" } */
>>>> +
>>>> +int g(int *, int *);
>>>> +int f()
>>>> +{
>>>> + switch (0) {
>>>> + int x; /* { dg-warning "cannot be initialized with" } */
>>>> + int y; /* { dg-warning "cannot be initialized with" } */
>>>> + default:
>>>> + return g(&x, &y);
>>>> + }
>>>> +}
>>>> +
>>>> +int g1(int, int);
>>>> +int f1()
>>>> +{
>>>> + switch (0) {
>>>> + int x; /* { dg-warning "cannot be initialized with" } */
>>>> + int y; /* { dg-warning "cannot be initialized with" } */
>>>> + default:
>>>> + return g1(x, y);
>>>> + }
>>>> +}
>>>> +
>>>> +struct S
>>>> +{
>>>> + char a;
>>>> + int b;
>>>> +};
>>>> +int g2(int);
>>>> +int f2(int input)
>>>> +{
>>>> + switch (0) {
>>>> + struct S x; /* { dg-warning "cannot be initialized with" } */
>>>> + struct S y; /* { dg-warning "cannot be initialized with" } */
>>>> + default:
>>>> + return g2(input) + x.b + y.b;
>>>> + }
>>>> +}
>>>>
>>>
>>> --
>>> Richard Biener <rguent...@suse.de>
>>> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
>>> Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
>>
>>
>
> --
> Richard Biener <rguent...@suse.de>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
> Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
