Re: [PATCH] Fix up -Wreturn-type (PR c++/83045)

[Christophe Lyon <christophe.lyon@linaro.org>]

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Hi,


On 21 November 2017 at 18:23, Jeff Law <law@redhat.com> wrote:
> On 11/21/2017 06:52 AM, Jakub Jelinek wrote:
>> Hi!
>>
>> The C++ FE now emits __builtin_unreachable () with BUILTINS_LOCATION
>> on spots that return from functions/methods returning non-void without
>> proper return.  This breaks the -Wreturn-type warning, because we then
>> don't see any return stmt without argument on the edges to exit, instead
>> we see those __builtin_unreachable () calls at the end of blocks without
>> successors.
>>
>> I wonder if the C++ FE addition of __builtin_unreachable () shouldn't be
>> done only if (optimize).
>>
>> Anyway, this patch tweaks tree-cfg.c so that it recognizes those
>> __builtin_unreachable () calls and reports the -Wreturn-type warning
>> in those cases too (warning in the FE would be too early, we need to
>> optimize away unreachable code).
>>
>> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>>
>> The patch regresses g++.dg/gomp/declare-simd-1.C, but given that it revealed
>> a real bug, I'm not trying to work around it in the patch and will fix it up
>> incrementally instead.
>>
>> 2017-11-21  Jakub Jelinek  <jakub@redhat.com>
>>
>>       PR c++/83045
>>       * tree-cfg.c (pass_warn_function_return::execute): Formatting fix.
>>       Also warn if seen __builtin_unreachable () call with BUILTINS_LOCATION.
>>       Use LOCATION_LOCUS when comparing against UNKNOWN_LOCATION.
>>
>>       * c-c++-common/pr61405.c (fn0, fn1): Add return stmts.
>>       * c-c++-common/Wlogical-op-2.c (fn): Likewise.
>>       * g++.dg/debug/pr53466.C: Add -Wno-return-type to dg-options.
>>       * g++.dg/opt/combine.C: Likewise.
>>       * g++.dg/ubsan/return-3.C: Likewise.
>>       * g++.dg/pr59445.C: Likewise.
>>       * g++.dg/pr49847.C: Likewise.
>>       * g++.dg/ipa/pr61800.C: Likewise.
>>       * g++.dg/ipa/pr63470.C: Likewise.
>>       * g++.dg/ipa/pr68672-1.C: Likewise.
>>       * g++.dg/pr58438.C: Likewise.
>>       * g++.dg/torture/pr59265.C: Likewise.
>>       * g++.dg/tree-ssa/ssa-dse-2.C: Likewise.
>>       * g++.old-deja/g++.eh/catch13.C: Likewise.
>>       * g++.old-deja/g++.eh/crash1.C: Likewise.
>>       * g++.dg/tm/pr60004.C: Expect -Wreturn-type warning.
>>       * g++.dg/torture/pr55740.C: Likewise.
>>       * g++.dg/torture/pr43257.C: Likewise.
>>       * g++.dg/torture/pr64280.C: Likewise.
>>       * g++.dg/torture/pr54684.C: Likewise.
>>       * g++.dg/torture/pr56694.C: Likewise.
>>       * g++.dg/torture/pr68470.C: Likewise.
>>       * g++.dg/torture/pr60648.C: Likewise.
>>       * g++.dg/torture/pr71281.C: Likewise.
>>       * g++.dg/torture/pr52772.C: Add -Wno-return-type dg-additional-options.
>>       * g++.dg/torture/pr64669.C: Likewise.
>>       * g++.dg/torture/pr58369.C: Likewise.
>>       * g++.dg/torture/pr33627.C: Likewise.
>>       * g++.dg/torture/predcom-1.C: Add
>>       #pragma GCC diagnostic ignored "-Wreturn-type".
>>       * g++.dg/lto/20090221_0.C: Likewise.
>>       * g++.dg/lto/20091026-1_1.C: Likewise.
>>       * g++.dg/lto/pr54625-1_1.C: Likewise.
>>       * g++.dg/warn/pr83045.C: New test.
> OK.
> jeff

As an obvious follow-up, I have committed the usual fix to
gcc.target/arm/pr56184.C (added -Wno-return-type).

Christophe

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diff --git a/gcc/testsuite/gcc.target/arm/pr56184.C b/gcc/testsuite/gcc.target/arm/pr56184.C
index fd278d3..8244222 100644
--- a/gcc/testsuite/gcc.target/arm/pr56184.C
+++ b/gcc/testsuite/gcc.target/arm/pr56184.C
@@ -1,6 +1,6 @@
 /* { dg-do compile } */
 /* { dg-skip-if "incompatible options" { ! { arm_thumb1_ok || arm_thumb2_ok } } } */
-/* { dg-options "-fno-short-enums -O2 -mthumb -march=armv7-a -mfpu=neon -mfloat-abi=softfp -mtune=cortex-a9 -fno-section-anchors" } */
+/* { dg-options "-fno-short-enums -O2 -mthumb -march=armv7-a -mfpu=neon -mfloat-abi=softfp -mtune=cortex-a9 -fno-section-anchors -Wno-return-type" } */
 
 typedef unsigned int size_t;
 __extension__ typedef int __intptr_t;

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2017-11-22  Christophe Lyon  <christophe.lyon@linaro.org>

	* gcc.target/arm/pr56184.C: Add -Wno-return-type to dg-options.