[Bug c++/53431] C++ preprocessor ignores #pragma GCC diagnostic

["manu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53431

--- Comment #23 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #21)
> Now that you posted a complete example here:
> https://gcc.gnu.org/ml/gcc-help/2015-07/msg00070.html you seem to actually
> be hitting PR66290, not this one.

Sorry, I meant PR64079.
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From: "manu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/64079] %+D in diagnostics breaks pragma GCC diagnostic
Date: Thu, 23 Jul 2015 13:31:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64079

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |easyhack

--- Comment #4 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
BTW, changes like the above are trivial to implement and test, thus this is a
nice easy-hack for beginners.
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From: "noloader at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/53431] C++ preprocessor ignores #pragma GCC diagnostic
Date: Thu, 23 Jul 2015 13:40:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53431

--- Comment #24 from Jeffrey Walton <noloader at gmail dot com> ---
(In reply to Manuel López-Ibáñez from comment #23)
> (In reply to Manuel López-Ibáñez from comment #21)
> > Now that you posted a complete example here:
> > https://gcc.gnu.org/ml/gcc-help/2015-07/msg00070.html you seem to actually
> > be hitting PR66290, not this one.
> 
> Sorry, I meant PR64079.

NP. In that example I posted, I meant GCC_DIAGNOSTIC_AWARE, not
GCC_OPTIMIZE_AWARE. Sorry about that.
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Subject: [Bug target/66930] [5 Regression]: gengtype.c is miscompiled during stage2
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66930

--- Comment #10 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to Kazumoto Kojima from comment #6)
> Created attachment 36040 [details]
> .i file for gengtype.c
> 
> I've confirmed a miscompile for gengtype.c with -O1 on my 5/6
> compilers.  With them,
> 
>      if (union_p)
>        {
> 	 oprintf (d->of, "%*sbreak;\n", d->indent, "");
> 	 d->indent -= 2;
>        }
> 
> lines in gengtype.c:walk_type function are compiled like as:
> 
>         bf      .L2253
>         mov.l   .L2593,r7
>         mov.l   @(36,r12),r6
>         mov.l   .L2580,r5
>         mov.l   .L2595,r1
>         jsr     @r1
> 	...
> 
> i.e. the instruction testing union_p variable is removed.
> The resulted gengtype produces files without "break" in many
> cases.  Although it's the other way around with the reported
> full of "break" symptom, I think the both are the same issue.
> The deletion has happened in sh_split_movrt_negc_to_movt_xor
> which is called by movrt_negc insn_and_split.  It seems that
> that splitting is applied for the case
> 
> 	tst	reg,reg
> 	mov	#-1,reg1
> 	negc	reg1,reg1
>         ...
>         call ...
>         ...
> 	tst	reg,reg
> 
> and the last tst was removed.  Oleg, could you take a look into
> this?

Somehow I couldn't find the code patterns above in my version of the compiled
code, so I've compared the compiled asm code of gengtype.ii with
sh_split_movrt_negc_to_movt_xor and without (always returns false) at -O1 and
hit this diff:

without:
        mov.l   @(40,r15),r0
        cmp/eq  #5,r0
        mov     #-1,r0
        negc    r0,r0
        mov.b   r0,@(2,r8)
        mov     r12,r5
        mov.l   .L2664,r1
        jsr     @r1
        mov.l   @(8,r10),r4
        mov     r14,r0
        mov.b   r0,@(2,r8)
        mov.l   .L2631,r1
        jsr     @r1
        mov     r13,r4
        mov.l   @(40,r15),r0
        cmp/eq  #5,r0
        bf      .L2286

with:
        mov.l   @(44,r15),r0
        cmp/eq  #5,r0
        movt    r0
        xor     #1,r0
        mov.b   r0,@(2,r8)
        mov     r12,r5
        mov.l   .L2664,r1
        jsr     @r1
        mov.l   @(8,r10),r4
        mov     r14,r0
        mov.b   r0,@(2,r8)
        mov.l   .L2631,r1
        jsr     @r1
        mov     r13,r4
        bf      .L2286

The original idea of this transformation is to not clobber the T bit with the
negc-movrt insn and re-use the T bit later.  It seems that it's missing the
fact that the T bit is clobbered by calls.  The following seems to fix it:

Index: gcc/config/sh/sh.c
===================================================================
--- gcc/config/sh/sh.c  (revision 225987)
+++ gcc/config/sh/sh.c  (working copy)
@@ -13888,6 +13888,7 @@
       && !sh_insn_operands_modified_between_p (t_before_negc.insn,
                                               t_before_negc.insn,
                                               t_after_negc.insn)
+      && !modified_between_p (get_t_reg_rtx (), curr_insn, t_after_negc.insn)
       && !sh_unspec_insn_p (t_after_negc.insn)
       && !volatile_insn_p (PATTERN (t_after_negc.insn))
       && !side_effects_p (PATTERN (t_after_negc.insn))

I've added this code as part of PR 63986.  I've checked with make -k check-gcc
RUNTESTFLAGS="sh.exp --target_board=sh-sim\{-m2a/-mb,-m4/-ml,-m4/-mb}" that
there are no new SH specific fails, so I assume the patch above should be OK
(although all the checks should probably be combined to avoid walking the insns
repeatedly).  Could you please add it to your test run?  I'm sorry for this
nasty bug.  Obviously it's not only a problem for -O1 but for anything > -O0.
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From: "anders.granlund.0 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/66976] New: Compiler error for well-formed program with a definition of a constexpr function returning void
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf976

            Bug ID: 66976
           Summary: Compiler error for well-formed program with a
                    definition of a constexpr function returning void
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anders.granlund.0 at gmail dot com
  Target Milestone: ---

The following program (prog.cc in the command line below) is well-formed:

  constexpr void f() {}
  int main() {}

Note that the return type void is a literal type according to [basic.types]/10:

  http://eel.is/c++draft/basic.types#10

I compiled the program with the following command line:

  gcc prog.cc -std=c++11 -pedantic-errors

I expected to get no errors since the program is well-formed, but I got the
following error:

prog.cc: In function 'constexpr void f()':
prog.cc:1:16: error: invalid return type 'void' of constexpr function
'constexpr void f()'constexpr void f() {}
                ^

For comparison Clang accepts the program without errors.

Output for gcc -v (I think the bug quite independent of this however):

Using built-in specs.
COLLECT_GCC=/usr/local/gcc-head/bin/g++
COLLECT_LTO_WRAPPER=/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /home/heads/gcc/gcc-source/configure
--prefix=/usr/local/gcc-head --enable-languages=c,c++ --enable-lto
--disable-multilib --without-ppl --without-cloog-ppl --enable-checking=release
--disable-nls
Thread model: posix
gcc version 6.0.0 20150722 (experimental) (GCC)
COLLECT_GCC_OPTIONS='-o' 'prog.exe' '-std=c++11' '-pedantic-errors' '-v'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/cc1plus -quiet
-v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE prog.cc -quiet -dumpbase prog.cc
-mtune=generic -march=x86-64 -auxbase prog -pedantic-errors -std=c++11 -version
-o /tmp/ccE6wwKW.s
GNU C++11 (GCC) version 6.0.0 20150722 (experimental)
(x86_64-unknown-linux-gnu)
        compiled by GNU C version 6.0.0 20150722 (experimental), GMP version
5.1.2, MPFR version 3.1.2, MPC version 1.0.1
warning: GMP header version 5.1.2 differs from library version 5.0.2.
warning: MPFR header version 3.1.2 differs from library version 3.1.0-p3.
GGC heuristics: --param ggc-min-expand\x100 --param ggc-min-heapsize\x131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../include/c++/6.0.0

/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../include/c++/6.0.0/x86_64-unknown-linux-gnu

/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../include/c++/6.0.0/backward
 /usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/include
 /usr/local/include
 /usr/local/gcc-head/include
 /usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++11 (GCC) version 6.0.0 20150722 (experimental)
(x86_64-unknown-linux-gnu)
        compiled by GNU C version 6.0.0 20150722 (experimental), GMP version
5.1.2, MPFR version 3.1.2, MPC version 1.0.1
warning: GMP header version 5.1.2 differs from library version 5.0.2.
warning: MPFR header version 3.1.2 differs from library version 3.1.0-p3.
GGC heuristics: --param ggc-min-expand\x100 --param ggc-min-heapsize\x131072
Compiler executable checksum: 9115218d8690e08d2bbd8844106c0d12
COLLECT_GCC_OPTIONS='-o' 'prog.exe' '-std=c++11' '-pedantic-errors' '-v'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
 as -v --64 -o /tmp/cc8TSYhs.o /tmp/ccE6wwKW.s
GNU assembler version 2.22 (x86_64-linux-gnu) using BFD version (GNU Binutils
for Ubuntu) 2.22
COMPILER_PATH=/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/
LIBRARY_PATH=/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../lib64/:/lib/x86_64-linux-gnu/:/lib/../lib64/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib64/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-o' 'prog.exe' '-std=c++11' '-pedantic-errors' '-v'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/collect2
-plugin
/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/liblto_plugin.so
-plugin-opt=/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
-plugin-opt=-fresolution=/tmp/cc4yk1QX.res -plugin-opt=-pass-through=-lgcc_s
-plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lgcc
--eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o
prog.exe /usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o
/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/crtbegin.o
-L/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0
-L/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../lib64
-L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu
-L/usr/lib/../lib64
-L/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../.. -rpath
/usr/local/gcc-head/lib64 -lpthread /tmp/cc8TSYhs.o -lstdc++ -lm -lgcc_s -lgcc
-lc -lgcc_s -lgcc
/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/crtend.o
/usr/lib/x86_64-linux-gnu/crtn.o