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clang++ 11 compilation issues
From: |
Alexandre Duret-Lutz |
Subject: |
clang++ 11 compilation issues |
Date: |
Tue, 12 Jan 2021 11:37:33 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Hi,
I'm upgrading a project that used a 8-month-old copy of gnulib to
today's version, and testing the result with various compilers.
This is a C++17 project that is not internationalized and that
uses the following modules:
argmatch
argp
closeout
error
isatty
mkstemp
mkstemps
progname
secure_getenv
stpcpy
strverscmp
sys_wait
My copy of gnulib is also patched with a patch I sent in 2013:
https://lists.gnu.org/archive/html/bug-gnulib/2013-12/msg00106.html
I compile with -Werror.
Testing the result with clang++ 11.0.1-2 (Debian unstable), I observe
the following two issues:
(1) lib/argmatch.h includes lib/gettext.h which fails as follows
> clang++ -DHAVE_CONFIG_H -I. -I.. -I.. -I.. -I../buddy/src -I../lib -I../lib
> -W -Wall -Werror -Wint-to-void-pointer-cast -Wzero-as-null-pointer-constant
> -Wcast-align -Wpointer-arith -Wwrite-strings -Wcast-qual -DXTSTRINGDEFINES
> -Wdocumentation -Wmissing-declarations -Woverloaded-virtual
> -Wmisleading-indentation -Wimplicit-fallthrough -Wnull-dereference
> -Wsuggest-override -Wpedantic -fvisibility=hidden -fvisibility-inlines-hidden
> -DSPOT_BUILD -std=c++17 -g -O -MT autcross.o -MD -MP -MF .deps/autcross.Tpo
> -c -o autcross.o autcross.cc
> In file included from autcross.cc:34:
> In file included from ../lib/argmatch.h:31:
> ../lib/gettext.h:234:22: error: zero as null pointer constant
> [-Werror,-Wzero-as-null-pointer-constant]
> if (msg_ctxt_id != NULL)
> ^~~~
> nullptr
> /usr/lib/llvm-11/lib/clang/11.0.1/include/stddef.h:84:18: note: expanded from
> macro 'NULL'
> # define NULL __null
> ^
> In file included from autcross.cc:34:
> In file included from ../lib/argmatch.h:31:
> ../lib/gettext.h:282:22: error: zero as null pointer constant
> [-Werror,-Wzero-as-null-pointer-constant]
> if (msg_ctxt_id != NULL)
> ^~~~
> nullptr
> /usr/lib/llvm-11/lib/clang/11.0.1/include/stddef.h:84:18: note: expanded from
> macro 'NULL'
> # define NULL __null
> ^
> 2 errors generated.
Just replacing these two tests with "if (msg_ctxt_id)" gets rid of the issue.
(2) ARGMATCH_VERIFY ends up using _Static_assert which is a C11 keyword
that does not exist in C++. However static_assert exists in C++11
with two args, and since C++17 with one arg.
> clang++ -DHAVE_CONFIG_H -I. -I.. -I.. -I.. -I../buddy/src -I../lib -I../lib
> -W -Wall -Werror -Wint-to-void-pointer-cast -Wzero-as-null-pointer-constant
> -Wcast-align -Wpointer-arith -Wwrite-strings -Wcast-qual -DXTSTRINGDEFINES
> -Wdocumentation -Wmissing-declarations -Woverloaded-virtual
> -Wmisleading-indentation -Wimplicit-fallthrough -Wnull-dereference
> -Wsuggest-override -Wpedantic -fvisibility=hidden -fvisibility-inlines-hidden
> -DSPOT_BUILD -std=c++17 -g -O -MT common_aoutput.o -MD -MP -MF
> .deps/common_aoutput.Tpo -c -o common_aoutput.o common_aoutput.cc
> common_aoutput.cc:85:1: error: '_Static_assert' is a C11 extension
> [-Werror,-Wc11-extensions]
> ARGMATCH_VERIFY(check_args, check_types);
> ^
> ../lib/argmatch.h:45:5: note: expanded from macro 'ARGMATCH_VERIFY'
> verify (ARRAY_CARDINALITY (Arglist) == ARRAY_CARDINALITY (Vallist) + 1)
> ^
> ../lib/verify.h:289:20: note: expanded from macro 'verify'
> # define verify(R) _GL_VERIFY (R, "verify (" #R ")", -)
> ^
> ../lib/verify.h:229:41: note: expanded from macro '_GL_VERIFY'
> # define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
> ^
> common_aoutput.cc:397:7: error: '_Static_assert' is a C11 extension
> [-Werror,-Wc11-extensions]
> ARGMATCH_VERIFY(args, format);
> ^
> ../lib/argmatch.h:45:5: note: expanded from macro 'ARGMATCH_VERIFY'
> verify (ARRAY_CARDINALITY (Arglist) == ARRAY_CARDINALITY (Vallist) + 1)
> ^
> ../lib/verify.h:289:20: note: expanded from macro 'verify'
> # define verify(R) _GL_VERIFY (R, "verify (" #R ")", -)
> ^
> ../lib/verify.h:229:41: note: expanded from macro '_GL_VERIFY'
> # define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
> ^
> 2 errors generated.
to work around this, I've just changed the definition of _GL_VERIFY in
lib/verify.h from
> #if defined _GL_HAVE__STATIC_ASSERT
> # define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
> #else
> # define _GL_VERIFY(R, DIAGNOSTIC, ...) \
> extern int (*_GL_GENSYM (_gl_verify_function) (void)) \
> [_GL_VERIFY_TRUE (R, DIAGNOSTIC)]
> #endif
to
> #if defined __cpp_static_assert
> # define _GL_VERIFY(R, DIAGNOSTIC, ...) static_assert (R, DIAGNOSTIC)
> #elif defined _GL_HAVE__STATIC_ASSERT
> # define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
> #else
> # define _GL_VERIFY(R, DIAGNOSTIC, ...) \
> extern int (*_GL_GENSYM (_gl_verify_function) (void)) \
> [_GL_VERIFY_TRUE (R, DIAGNOSTIC)]
> #endif
However there are a few __cplusplus tests at the top of the file that
attempt to tell when _Static_assert can be used (and failed here), and I
do not really follow that logic. Those macros check for
__cpp_static_assert to assume something about _Static_assert, which
seems dubious.
--
Alexandre Duret-Lutz
- clang++ 11 compilation issues,
Alexandre Duret-Lutz <=