[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[arthur.j.odwyer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61613

--- Comment #1 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> ---
Already filed against Clang: http://llvm.org/bugs/show_bug.cgi?id=19141

[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61613

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-06-26
     Ever confirmed|0                           |1
      Known to fail|                            |3.2.3, 4.3.4, 4.9.0

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed with 4.9.0.  2.95 prints

t.c:3: badly punctuated parameter list in `#define'

[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[potswa at mac dot com]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61613

David Krauss <potswa at mac dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |potswa at mac dot com

--- Comment #3 from David Krauss <potswa at mac dot com> ---
The surprising result is because you passed print to itself, and the ##
operator disables pre-expansion of argument tokens. If you want to expand
print(print(…)), you can use the double-expansion idiom used for other special
macros.

#define do_print(x,...) (print(1,"macro"),print(1, ##__VA_ARGS__))
#define print(...) do_print( __VA_ARGS__ )

GCC 2.95 is not a role model. Regardless of what future compilers do, you
should suggest the above fix to the Boost.ScopeExit maintainer.

Note that I plan to propose the current behavior for standardization; see
http://open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3882.pdf . (It is dated in
the past, but it has not been processed yet due to a technicality.) Your use
case does sound quite reasonable, but unless the implementations move soon, the
door might shut as it ceases to have the flexibility of a GCC extension.

On the other hand, if GCC does change here, I'll be compelled to propose
standardizing the update instead.
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From: "zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/62078] New: [4.10 Regression] ICE: verify_flow_info failed: missing REG_EH_REGION note at the end of bb 2 with -fdelete-dead-exceptions
Date: Sun, 10 Aug 2014 09:39:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idb078

            Bug ID: 62078
           Summary: [4.10 Regression] ICE: verify_flow_info failed:
                    missing REG_EH_REGION note at the end of bb 2 with
                    -fdelete-dead-exceptions
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz

Created attachment 33278
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id3278&actioníit
mostly reduced testcase

Compiler output:
$ $ /mnt/svn/gcc-trunk/binary-latest/bin/gcc -Og -fdelete-dead-exceptions
-fnon-call-exceptions testcase.C
testcase.C: In function 'void foo()':
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 40
 }
 ^
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 38
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 36
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 34
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 32
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 30
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 28
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 26
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 24
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 22
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 18
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 16
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 14
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 12
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 10
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 8
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 6
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 4
testcase.C:31:1: error: missing REG_EH_REGION note at the end of bb 2
testcase.C:31:1: internal compiler error: verify_flow_info failed
0x91f1d6 verify_flow_info()
        /mnt/svn/gcc-trunk/gcc/cfghooks.c:260
0xc28ac4 execute_function_todo
        /mnt/svn/gcc-trunk/gcc/passes.c:1761
0xc294d3 execute_todo
        /mnt/svn/gcc-trunk/gcc/passes.c:1806
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

(gdb) bt
#0  internal_error (gmsgid=gmsgid@entry=0x16e67fb "verify_flow_info failed") at
/mnt/svn/gcc-trunk/gcc/diagnostic.c:1130
#1  0x000000000091f1d7 in verify_flow_info () at
/mnt/svn/gcc-trunk/gcc/cfghooks.c:260
#2  0x0000000000c28ac5 in execute_function_todo (fn=0x7ffff6dfc498,
data=<optimized out>) at /mnt/svn/gcc-trunk/gcc/passes.c:1761
#3  0x0000000000c294d4 in execute_todo (flags\x131136) at
/mnt/svn/gcc-trunk/gcc/passes.c:1806
#4  0x0000000000c2b86e in execute_one_pass (pass=pass@entry=0x1f9f350) at
/mnt/svn/gcc-trunk/gcc/passes.c:2162
#5  0x0000000000c2bdb6 in execute_pass_list_1 (pass=0x1f9f350) at
/mnt/svn/gcc-trunk/gcc/passes.c:2201
#6  0x0000000000c2bdc8 in execute_pass_list_1 (pass=0x1f9e9f0,
pass@entry=0x1f9b930) at /mnt/svn/gcc-trunk/gcc/passes.c:2202
#7  0x0000000000c2be09 in execute_pass_list (fn=0x7ffff6dfc498, pass=0x1f9b930)
at /mnt/svn/gcc-trunk/gcc/passes.c:2212
#8  0x000000000094ab40 in expand_function (node=node@entry=0x7ffff6aa7450) at
/mnt/svn/gcc-trunk/gcc/cgraphunit.c:1776
#9  0x000000000094c20c in expand_all_functions () at
/mnt/svn/gcc-trunk/gcc/cgraphunit.c:1910
#10 compile () at /mnt/svn/gcc-trunk/gcc/cgraphunit.c:2254
#11 0x000000000094dba5 in finalize_compilation_unit () at
/mnt/svn/gcc-trunk/gcc/cgraphunit.c:2331
#12 0x000000000072a166 in cp_write_global_declarations () at
/mnt/svn/gcc-trunk/gcc/cp/decl2.c:4644
#13 0x0000000000d268bd in compile_file () at
/mnt/svn/gcc-trunk/gcc/toplev.c:562
#14 0x0000000000d28c05 in do_compile () at /mnt/svn/gcc-trunk/gcc/toplev.c:1947
#15 toplev_main (argc\x16, argv=0x7fffffffd7b8) at
/mnt/svn/gcc-trunk/gcc/toplev.c:2023
#16 0x00007ffff6e67db5 in __libc_start_main () from /lib64/libc.so.6
#17 0x000000000063e401 in _start ()

According to PR61031#c1, this might be just exposed by extended checking in
4.10.

Tested revisions:
r213777 - ICE
4_9 r212703 - OK

[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[potswa at mac dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61613

--- Comment #4 from David Krauss <potswa at mac dot com> ---
Created attachment 33288
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33288&action=edit
Fix

Well, I decided to Do The Right Thing for users. Here is a working patch.

Let's see what the maintainers do with it :) .

[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[potswa at mac dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61613

--- Comment #6 from David Krauss <potswa at mac dot com> ---
The patch should already pass the coding standards. I'm already legally
registered as a contributor.

Arthur, can you take care of the rest of the process? (Did you get my email?)

I'd like to take it 100% but the testsuite isn't working on my system. The
patch is small enough and unobscure enough that it's easier for someone else to
take responsibility than for me to dedicate another day to GCC build
configuration.

[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[arthur.j.odwyer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61613

--- Comment #7 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> ---
@David, sadly, I'm not set up to build or test GCC patches, nor am I registered
as a contributor. Anyone else want to step up?

I could suggest test cases, perhaps, but I wouldn't be good at shepherding this
patch all the way through the process-I've-never-done-before.

[Bug preprocessor/61613] ,##__VA_ARGS__ fails to expand the first variadic argument if it is a macro-name

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61613

--- Comment #8 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to David Krauss from comment #6)
> I'd like to take it 100% but the testsuite isn't working on my system. The
> patch is small enough and unobscure enough that it's easier for someone else
> to take responsibility than for me to dedicate another day to GCC build
> configuration.

If you are a sporadic contributor, the easiest and cheapest way to work on GCC
is to get an account in the compile farm: https://gcc.gnu.org/wiki/CompileFarm
and use one of the many scripts in contrib/ (or my own gccfarming script:
https://gcc.gnu.org/wiki/ManuelL%C3%B3pezIb%C3%A1%C3%B1ez?action=AttachFile&do=view&target=gccfarming)
to bootstrap and regression test patches.
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Subject: [Bug other/60465] Compiling glibc-2.17,2.18 with gcc-4.8.2 and binutils-2.23.2,2.24 results in segfaults in _start / elf_get_dynamic_info
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id`465

--- Comment #9 from Mike Frysinger <vapier at gentoo dot org> ---
i've verified that 4.8.0 & 4.9.1 fail as well :/

binutils 2.24 doesn't help