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author | Qing Zhao <qing.zhao@oracle.com> | 2022-03-02 16:48:37 +0000 |
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committer | Qing Zhao <qing.zhao@oracle.com> | 2022-03-02 16:53:00 +0000 |
commit | dbaabd06aaf4a1b0f2a20671c39148a0bd6ccf0e (patch) | |
tree | da157c6ccb1c857e58b7e4521fde2bd561351390 /gcc/common.opt | |
parent | 8fede2876a751d53a28442dcca32466daa929daa (diff) | |
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Don't emit switch-unreachable warnings for -ftrivial-auto-var-init (PR102276)
At the same time, adding -Wtrivial-auto-var-init and update documentation.
-Wtrivial-auto-var-init and update documentation.
for the following testing case:
1 int g(int *);
2 int f1()
3 {
4 switch (0) {
5 int x;
6 default:
7 return g(&x);
8 }
9 }
compiling with -O -ftrivial-auto-var-init causes spurious warning:
warning: statement will never be executed [-Wswitch-unreachable]
5 | int x;
| ^
This is due to the compiler-generated initialization at the point of
the declaration.
We could avoid the warning to exclude the following cases:
when
flag_auto_var_init > AUTO_INIT_UNINITIALIZED
And
1) call to .DEFERRED_INIT
2) call to __builtin_clear_padding if the 2nd argument is present and non-zero
3) a gimple assign store right after the .DEFERRED_INIT call that has the LHS
as RHS
However, we still need to warn users about the incapability of the option
-ftrivial-auto-var-init by adding a new warning option -Wtrivial-auto-var-init
to report cases when it 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.
gcc/ChangeLog:
PR middle-end/102276
* 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 (emit_warn_switch_unreachable): New function.
(warn_switch_unreachable_r): Rename to ...
(warn_switch_unreachable_and_auto_init_r): This.
(maybe_warn_switch_unreachable): Rename to ...
(maybe_warn_switch_unreachable_and_auto_init): This.
(gimplify_switch_expr): Update calls to renamed function.
gcc/testsuite/ChangeLog:
PR middle-end/102276
* gcc.dg/auto-init-pr102276-1.c: New test.
* gcc.dg/auto-init-pr102276-2.c: New test.
* gcc.dg/auto-init-pr102276-3.c: New test.
* gcc.dg/auto-init-pr102276-4.c: New test.
Diffstat (limited to 'gcc/common.opt')
-rw-r--r-- | gcc/common.opt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/gcc/common.opt b/gcc/common.opt index c21e527..8b6513d 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 cases where -ftrivial-auto-var-init cannot initialize an auto variable. + 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. |