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fix interaction between 'extern-inline' and 'warn-on-use' modules
From: |
Bruno Haible |
Subject: |
fix interaction between 'extern-inline' and 'warn-on-use' modules |
Date: |
Sun, 05 Aug 2018 14:14:38 +0200 |
User-agent: |
KMail/5.1.3 (Linux/4.4.0-130-generic; KDE/5.18.0; x86_64; ; ) |
When running the documented recipe for use of the 'posixcheck' module on
GNU hello, I'm getting this link error:
gcc -g -O2 -o hello src/hello.o ./lib/libhello.a
./lib/libhello.a(closeout.o): In function `rpl_environ':
/media/develdata/devel/HELLO/hello/lib/unistd.h:890: multiple definition of
`rpl_environ'
src/hello.o:/media/develdata/devel/HELLO/hello/lib/unistd.h:890: first defined
here
collect2: error: ld returned 1 exit status
Makefile:2410: recipe for target 'hello' failed
make[2]: *** [hello] Error 1
The reason is that 3 object files export the 'rpl_environ' symbol:
$ nm lib/unistd.o | grep environ
U environ
0000000000000000 T rpl_environ
$ nm lib/closeout.o | grep environ
U environ
0000000000000000 T rpl_environ
$ nm src/hello.o | grep environ
U environ
00000000000001c0 T rpl_environ
The cause is the 'extern' storage class specifier in the _GL_WARN_ON_USE
macro, that silently transforms
inline char *** rpl_environ (void) { ... }
to
extern inline char *** rpl_environ (void) { ... }
This patch fixes it.
2018-08-05 Bruno Haible <address@hidden>
Fix link error regarding 'rpl_environ' (regression from 2012-11-21).
* m4/extern-inline.m4: Add more comments.
* lib/warn-on-use.h (_GL_WARN_ON_USE_ATTRIBUTE): New macro.
* lib/unistd.in.h (rpl_environ): Use it instead of _GL_WARN_ON_USE.
* lib/math.in.h (_GL_WARN_REAL_FLOATING_DECL): Likewise.
diff --git a/m4/extern-inline.m4 b/m4/extern-inline.m4
index da8a2cc..3661cbd 100644
--- a/m4/extern-inline.m4
+++ b/m4/extern-inline.m4
@@ -25,7 +25,8 @@ AC_DEFUN([gl_EXTERN_INLINE],
if isdigit is mistakenly implemented via a static inline function,
a program containing an extern inline function that calls isdigit
may not work since the C standard prohibits extern inline functions
- from calling static functions. This bug is known to occur on:
+ from calling static functions (ISO C 99 section 6.7.4.(3).
+ This bug is known to occur on:
OS X 10.8 and earlier; see:
https://lists.gnu.org/r/bug-gnulib/2012-12/msg00023.html
@@ -38,7 +39,18 @@ AC_DEFUN([gl_EXTERN_INLINE],
OS X 10.9 has a macro __header_inline indicating the bug is fixed for C and
for clang but remains for g++; see <https://trac.macports.org/ticket/41033>.
- Assume DragonFly and FreeBSD will be similar. */
+ Assume DragonFly and FreeBSD will be similar.
+
+ GCC 4.3 and above with -std=c99 or -std=gnu99 implements ISO C99
+ inline semantics, unless -fgnu89-inline is used. It defines a macro
+ __GNUC_STDC_INLINE__ to indicate this situation or a macro
+ __GNUC_GNU_INLINE__ to indicate the opposite situation.
+ GCC 4.2 with -std=c99 or -std=gnu99 implements the GNU C inline
+ semantics but warns, unless -fgnu89-inline is used:
+ warning: C99 inline functions are not supported; using GNU89
+ warning: to disable this warning use -fgnu89-inline or the gnu_inline
function attribute
+ It defines a macro __GNUC_GNU_INLINE__ to indicate this situation.
+ */
#if (((defined __APPLE__ && defined __MACH__) \
|| defined __DragonFly__ || defined __FreeBSD__) \
&& (defined __header_inline \
diff --git a/lib/warn-on-use.h b/lib/warn-on-use.h
index 173e2a4..b000dcc 100644
--- a/lib/warn-on-use.h
+++ b/lib/warn-on-use.h
@@ -20,23 +20,32 @@
supported by the compiler. If the compiler does not support this
feature, the macro expands to an unused extern declaration.
- This macro is useful for marking a function as a potential
+ _GL_WARN_ON_USE_ATTRIBUTE ("literal string") expands to the
+ attribute used in _GL_WARN_ON_USE. If the compiler does not support
+ this feature, it expands to empty.
+
+ These macros are useful for marking a function as a potential
portability trap, with the intent that "literal string" include
instructions on the replacement function that should be used
- instead. However, one of the reasons that a function is a
- portability trap is if it has the wrong signature. Declaring
- FUNCTION with a different signature in C is a compilation error, so
- this macro must use the same type as any existing declaration so
- that programs that avoid the problematic FUNCTION do not fail to
- compile merely because they included a header that poisoned the
- function. But this implies that _GL_WARN_ON_USE is only safe to
- use if FUNCTION is known to already have a declaration. Use of
- this macro implies that there must not be any other macro hiding
- the declaration of FUNCTION; but undefining FUNCTION first is part
- of the poisoning process anyway (although for symbols that are
- provided only via a macro, the result is a compilation error rather
- than a warning containing "literal string"). Also note that in
- C++, it is only safe to use if FUNCTION has no overloads.
+ instead.
+ _GL_WARN_ON_USE is for functions with 'extern' linkage.
+ _GL_WARN_ON_USE_ATTRIBUTE is for functions with 'static' or 'inline'
+ linkage.
+
+ However, one of the reasons that a function is a portability trap is
+ if it has the wrong signature. Declaring FUNCTION with a different
+ signature in C is a compilation error, so this macro must use the
+ same type as any existing declaration so that programs that avoid
+ the problematic FUNCTION do not fail to compile merely because they
+ included a header that poisoned the function. But this implies that
+ _GL_WARN_ON_USE is only safe to use if FUNCTION is known to already
+ have a declaration. Use of this macro implies that there must not
+ be any other macro hiding the declaration of FUNCTION; but
+ undefining FUNCTION first is part of the poisoning process anyway
+ (although for symbols that are provided only via a macro, the result
+ is a compilation error rather than a warning containing
+ "literal string"). Also note that in C++, it is only safe to use if
+ FUNCTION has no overloads.
For an example, it is possible to poison 'getline' by:
- adding a call to gl_WARN_ON_USE_PREPARE([[#include <stdio.h>]],
@@ -54,12 +63,21 @@
(less common usage, like &environ, will cause a compilation error
rather than issue the nice warning, but the end result of informing
the developer about their portability problem is still achieved):
- #if HAVE_RAW_DECL_ENVIRON
- static char ***rpl_environ (void) { return &environ; }
- _GL_WARN_ON_USE (rpl_environ, "environ is not always properly declared");
- # undef environ
- # define environ (*rpl_environ ())
- #endif
+ #if HAVE_RAW_DECL_ENVIRON
+ static char ***
+ rpl_environ (void) { return &environ; }
+ _GL_WARN_ON_USE (rpl_environ, "environ is not always properly declared");
+ # undef environ
+ # define environ (*rpl_environ ())
+ #endif
+ or better (avoiding contradictory use of 'static' and 'extern'):
+ #if HAVE_RAW_DECL_ENVIRON
+ static char ***
+ _GL_WARN_ON_USE_ATTRIBUTE ("environ is not always properly declared")
+ rpl_environ (void) { return &environ; }
+ # undef environ
+ # define environ (*rpl_environ ())
+ #endif
*/
#ifndef _GL_WARN_ON_USE
@@ -67,13 +85,17 @@
/* A compiler attribute is available in gcc versions 4.3.0 and later. */
# define _GL_WARN_ON_USE(function, message) \
extern __typeof__ (function) function __attribute__ ((__warning__ (message)))
+# define _GL_WARN_ON_USE_ATTRIBUTE(message) \
+ __attribute__ ((__warning__ (message)))
# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
/* Verify the existence of the function. */
# define _GL_WARN_ON_USE(function, message) \
extern __typeof__ (function) function
+# define _GL_WARN_ON_USE_ATTRIBUTE(message)
# else /* Unsupported. */
# define _GL_WARN_ON_USE(function, message) \
_GL_WARN_EXTERN_C int _gl_warn_on_use
+# define _GL_WARN_ON_USE_ATTRIBUTE(message)
# endif
#endif
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index 075cab3..8098291 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -432,12 +432,12 @@ extern char **environ;
#elif defined GNULIB_POSIXCHECK
# if HAVE_RAW_DECL_ENVIRON
_GL_UNISTD_INLINE char ***
+_GL_WARN_ON_USE_ATTRIBUTE ("environ is unportable - "
+ "use gnulib module environ for portability")
rpl_environ (void)
{
return &environ;
}
-_GL_WARN_ON_USE (rpl_environ, "environ is unportable - "
- "use gnulib module environ for portability");
# undef environ
# define environ (*rpl_environ ())
# endif
diff --git a/lib/math.in.h b/lib/math.in.h
index 053d4e1..c30fc20 100644
--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -92,27 +92,27 @@ _GL_END_NAMESPACE
classification macros with an argument of real-floating (that is,
one of float, double, or long double). */
#define _GL_WARN_REAL_FLOATING_DECL(func) \
-_GL_MATH_INLINE int \
-rpl_ ## func ## f (float f) \
-{ \
- return func (f); \
-} \
-_GL_MATH_INLINE int \
-rpl_ ## func ## d (double d) \
-{ \
- return func (d); \
-} \
-_GL_MATH_INLINE int \
-rpl_ ## func ## l (long double l) \
-{ \
- return func (l); \
-} \
-_GL_WARN_ON_USE (rpl_ ## func ## f, #func " is unportable - " \
- "use gnulib module " #func " for portability"); \
-_GL_WARN_ON_USE (rpl_ ## func ## d, #func " is unportable - " \
- "use gnulib module " #func " for portability"); \
-_GL_WARN_ON_USE (rpl_ ## func ## l, #func " is unportable - " \
- "use gnulib module " #func " for portability")
+_GL_MATH_INLINE int \
+_GL_WARN_ON_USE_ATTRIBUTE (#func " is unportable - " \
+ "use gnulib module " #func " for portability") \
+rpl_ ## func ## f (float f) \
+{ \
+ return func (f); \
+} \
+_GL_MATH_INLINE int \
+_GL_WARN_ON_USE_ATTRIBUTE (#func " is unportable - " \
+ "use gnulib module " #func " for portability") \
+rpl_ ## func ## d (double d) \
+{ \
+ return func (d); \
+} \
+_GL_MATH_INLINE int \
+_GL_WARN_ON_USE_ATTRIBUTE (#func " is unportable - " \
+ "use gnulib module " #func " for portability") \
+rpl_ ## func ## l (long double l) \
+{ \
+ return func (l); \
+}
#define _GL_WARN_REAL_FLOATING_IMPL(func, value) \
(sizeof (value) == sizeof (float) ? rpl_ ## func ## f (value) \
: sizeof (value) == sizeof (double) ? rpl_ ## func ## d (value) \
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- fix interaction between 'extern-inline' and 'warn-on-use' modules,
Bruno Haible <=