Re: GNULIB_POSIXCHECK and C++

[Bruno Haible]

Tom G. Christensen wrote:
> > Generally, these C++ tests are supported on glibc systems with
> > modern GCC. For testing Solaris 10, try passing the option
> > '--without-c++-tests' to gnulib-tool.
> > 
> 
> This does not seem to have any effect.
> 
> I tried running gnulib-tool like this:
> ./gnulib-tool --create-testdir --dir=./testdir --single-configure 
> --without-privileged-tests --without-c++-tests
> 
> However the testdir still includes the C++ tests.
> 
> To avoid the C++ tests I needed to pass the option '--disable-c++' to 
> ./configure.

OK, so I guessed wrong regarding the cause of the problem.

Did some experiments, and it seems the cause is the combination of the
'posixcheck' module and C++.  With a testdir created through

./gnulib-tool --create-testdir --dir=../testdir1 --single-configure 
--with-c++-tests \
  array-list  avltreehash-list avltree-list carray-list linkedhash-list \
  linked-list list rbtreehash-list rbtree-list sublist xlist xsublist list-c++ \
  posixcheck strpbrk

I get compilation errors even on glibc systems:


In file included from ../../gltests/test-list-c++.cc:23:0:
../gllib/string.h:660:1: error: type of ‘memchr’ is unknown
 _GL_WARN_ON_USE (memchr, "memchr has platform-specific bugs - "
 ^
../gllib/string.h:660:1: error: ‘int memchr’ redeclared as different kind of 
symbol
 _GL_WARN_ON_USE (memchr, "memchr has platform-specific bugs - "
 ^
In file included from ../gllib/string.h:41:0,
                 from ../../gltests/test-list-c++.cc:23:
/usr/include/string.h:85:1: note: previous declaration ‘const void* 
memchr(const void*, int, size_t)’
 memchr (const void *__s, int __c, size_t __n) __THROW
 ^
In file included from ../../gltests/test-list-c++.cc:23:0:
../gllib/string.h:744:1: error: type of ‘memrchr’ is unknown
 _GL_WARN_ON_USE (memrchr, "memrchr is unportable - "
 ^
../gllib/string.h:744:1: error: ‘int memrchr’ redeclared as different kind of 
symbol
 _GL_WARN_ON_USE (memrchr, "memrchr is unportable - "
 ^
In file included from ../gllib/string.h:41:0,
                 from ../../gltests/test-list-c++.cc:23:
/usr/include/string.h:114:26: note: previous declaration ‘const void* 
memrchr(const void*, int, size_t)’
 extern "C++" const void *memrchr (const void *__s, int __c, size_t __n)
                          ^
In file included from ../../gltests/test-list-c++.cc:23:0:
../gllib/string.h:774:1: error: type of ‘rawmemchr’ is unknown
 _GL_WARN_ON_USE (rawmemchr, "rawmemchr is unportable - "
 ^
../gllib/string.h:774:1: error: ‘int rawmemchr’ redeclared as different kind of 
symbol
 _GL_WARN_ON_USE (rawmemchr, "rawmemchr is unportable - "
 ^
In file included from ../gllib/string.h:41:0,
                 from ../../gltests/test-list-c++.cc:23:
/usr/include/string.h:103:26: note: previous declaration ‘const void* 
rawmemchr(const void*, int)’
 extern "C++" const void *rawmemchr (const void *__s, int __c)
                          ^
In file included from ../../gltests/test-list-c++.cc:23:0:
../gllib/string.h:878:1: error: type of ‘strchrnul’ is unknown
 _GL_WARN_ON_USE (strchrnul, "strchrnul is unportable - "
 ^
../gllib/string.h:878:1: error: ‘int strchrnul’ redeclared as different kind of 
symbol
 _GL_WARN_ON_USE (strchrnul, "strchrnul is unportable - "
 ^
In file included from ../gllib/string.h:41:0,
                 from ../../gltests/test-list-c++.cc:23:
/usr/include/string.h:269:26: note: previous declaration ‘const char* 
strchrnul(const char*, int)’
 extern "C++" const char *strchrnul (const char *__s, int __c)
                          ^
In file included from ../../gltests/test-list-c++.cc:23:0:
../gllib/string.h:1151:1: error: type of ‘strstr’ is unknown
 _GL_WARN_ON_USE (strstr, "strstr is quadratic on many systems, and cannot "
 ^
../gllib/string.h:1151:1: error: ‘int strstr’ redeclared as different kind of 
symbol
 _GL_WARN_ON_USE (strstr, "strstr is quadratic on many systems, and cannot "
 ^
In file included from ../gllib/string.h:41:0,
                 from ../../gltests/test-list-c++.cc:23:
/usr/include/string.h:330:1: note: previous declaration ‘const char* 
strstr(const char*, const char*)’
 strstr (const char *__haystack, const char *__needle) __THROW
 ^
In file included from ../../gltests/test-list-c++.cc:23:0:
../gllib/string.h:1199:1: error: type of ‘strcasestr’ is unknown
 _GL_WARN_ON_USE (strcasestr, "strcasestr does work correctly on character "
 ^
../gllib/string.h:1199:1: error: ‘int strcasestr’ redeclared as different kind 
of symbol
 _GL_WARN_ON_USE (strcasestr, "strcasestr does work correctly on character "
 ^
In file included from ../gllib/string.h:41:0,
                 from ../../gltests/test-list-c++.cc:23:
/usr/include/string.h:364:26: note: previous declaration ‘const char* 
strcasestr(const char*, const char*)’
 extern "C++" const char *strcasestr (const char *__haystack,
                          ^


That's too much effort to fix, given that C++ mode is only of secondary
importance to Gnulib. I'm therefore disabling this combination:


2020-11-17  Bruno Haible  <bruno@clisp.org>

        posixcheck: Don't enable GNULIB_POSIXCHECK in C++ mode.
        Reported by Tom G. Christensen <tgc@jupiterrise.com> in
        <https://lists.gnu.org/archive/html/bug-gnulib/2020-11/msg00062.html>.
        * m4/posixcheck.m4 (gl_POSIXCHECK): Don't define GNULIB_POSIXCHECK in
        C++ mode.

diff --git a/m4/posixcheck.m4 b/m4/posixcheck.m4
index d9a3d6c..2ee1b25 100644
--- a/m4/posixcheck.m4
+++ b/m4/posixcheck.m4
@@ -6,7 +6,11 @@ dnl with or without modifications, as long as this notice is 
preserved.
 
 AC_DEFUN([gl_POSIXCHECK],
 [
-  AC_DEFINE([GNULIB_POSIXCHECK], [1],
-    [Define to enable warnings for determining which Gnulib modules to use,
-     for portability of POSIX functions.])
+  AH_VERBATIM([POSIXCHECK],
+    [/* Define to enable warnings for determining which Gnulib modules to use, 
for
+   portability of POSIX functions.  This does not work well in C++ mode.  */
+#ifndef __cplusplus
+# define GNULIB_POSIXCHECK 1
+#endif
+])
 ])