mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-21 10:24:55 +00:00
110 lines
5.0 KiB
C
110 lines
5.0 KiB
C
/* A C macro for emitting warnings if a function is used.
|
|
Copyright (C) 2010-2011 Free Software Foundation, Inc.
|
|
|
|
This program is free software: you can redistribute it and/or modify it
|
|
under the terms of the GNU General Public License as published
|
|
by the Free Software Foundation; either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>. */
|
|
|
|
/* _GL_WARN_ON_USE (function, "literal string") issues a declaration
|
|
for FUNCTION which will then trigger a compiler warning containing
|
|
the text of "literal string" anywhere that function is called, if
|
|
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
|
|
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.
|
|
|
|
For an example, it is possible to poison 'getline' by:
|
|
- adding a call to gl_WARN_ON_USE_PREPARE([[#include <stdio.h>]],
|
|
[getline]) in configure.ac, which potentially defines
|
|
HAVE_RAW_DECL_GETLINE
|
|
- adding this code to a header that wraps the system <stdio.h>:
|
|
#undef getline
|
|
#if HAVE_RAW_DECL_GETLINE
|
|
_GL_WARN_ON_USE (getline, "getline is required by POSIX 2008, but"
|
|
"not universally present; use the gnulib module getline");
|
|
#endif
|
|
|
|
It is not possible to directly poison global variables. But it is
|
|
possible to write a wrapper accessor function, and poison that
|
|
(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 inline 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
|
|
*/
|
|
#ifndef _GL_WARN_ON_USE
|
|
|
|
# if 4 < __GNUC__ || (__GNUC__ == 4 && 3 <= __GNUC_MINOR__)
|
|
/* 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)))
|
|
# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
|
|
/* Verify the existence of the function. */
|
|
# define _GL_WARN_ON_USE(function, message) \
|
|
extern __typeof__ (function) function
|
|
# else /* Unsupported. */
|
|
# define _GL_WARN_ON_USE(function, message) \
|
|
_GL_WARN_EXTERN_C int _gl_warn_on_use
|
|
# endif
|
|
#endif
|
|
|
|
/* _GL_WARN_ON_USE_CXX (function, rettype, parameters_and_attributes, "string")
|
|
is like _GL_WARN_ON_USE (function, "string"), except that the function is
|
|
declared with the given prototype, consisting of return type, parameters,
|
|
and attributes.
|
|
This variant is useful for overloaded functions in C++. _GL_WARN_ON_USE does
|
|
not work in this case. */
|
|
#ifndef _GL_WARN_ON_USE_CXX
|
|
# if 4 < __GNUC__ || (__GNUC__ == 4 && 3 <= __GNUC_MINOR__)
|
|
# define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \
|
|
extern rettype function parameters_and_attributes \
|
|
__attribute__ ((__warning__ (msg)))
|
|
# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
|
|
/* Verify the existence of the function. */
|
|
# define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \
|
|
extern rettype function parameters_and_attributes
|
|
# else /* Unsupported. */
|
|
# define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \
|
|
_GL_WARN_EXTERN_C int _gl_warn_on_use
|
|
# endif
|
|
#endif
|
|
|
|
/* _GL_WARN_EXTERN_C declaration;
|
|
performs the declaration with C linkage. */
|
|
#ifndef _GL_WARN_EXTERN_C
|
|
# if defined __cplusplus
|
|
# define _GL_WARN_EXTERN_C extern "C"
|
|
# else
|
|
# define _GL_WARN_EXTERN_C extern
|
|
# endif
|
|
#endif
|