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Diffstat (limited to 'build-aux/snippet/warn-on-use.h')
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diff --git a/build-aux/snippet/warn-on-use.h b/build-aux/snippet/warn-on-use.h deleted file mode 100644 index 1736a1bd..00000000 --- a/build-aux/snippet/warn-on-use.h +++ /dev/null | |||
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1 | /* A C macro for emitting warnings if a function is used. | ||
2 | Copyright (C) 2010-2013 Free Software Foundation, Inc. | ||
3 | |||
4 | This program is free software: you can redistribute it and/or modify it | ||
5 | under the terms of the GNU General Public License as published | ||
6 | by the Free Software Foundation; either version 3 of the License, or | ||
7 | (at your option) any later version. | ||
8 | |||
9 | This program is distributed in the hope that it will be useful, | ||
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
12 | General Public License for more details. | ||
13 | |||
14 | You should have received a copy of the GNU General Public License | ||
15 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ | ||
16 | |||
17 | /* _GL_WARN_ON_USE (function, "literal string") issues a declaration | ||
18 | for FUNCTION which will then trigger a compiler warning containing | ||
19 | the text of "literal string" anywhere that function is called, if | ||
20 | supported by the compiler. If the compiler does not support this | ||
21 | feature, the macro expands to an unused extern declaration. | ||
22 | |||
23 | This macro is useful for marking a function as a potential | ||
24 | portability trap, with the intent that "literal string" include | ||
25 | instructions on the replacement function that should be used | ||
26 | instead. However, one of the reasons that a function is a | ||
27 | portability trap is if it has the wrong signature. Declaring | ||
28 | FUNCTION with a different signature in C is a compilation error, so | ||
29 | this macro must use the same type as any existing declaration so | ||
30 | that programs that avoid the problematic FUNCTION do not fail to | ||
31 | compile merely because they included a header that poisoned the | ||
32 | function. But this implies that _GL_WARN_ON_USE is only safe to | ||
33 | use if FUNCTION is known to already have a declaration. Use of | ||
34 | this macro implies that there must not be any other macro hiding | ||
35 | the declaration of FUNCTION; but undefining FUNCTION first is part | ||
36 | of the poisoning process anyway (although for symbols that are | ||
37 | provided only via a macro, the result is a compilation error rather | ||
38 | than a warning containing "literal string"). Also note that in | ||
39 | C++, it is only safe to use if FUNCTION has no overloads. | ||
40 | |||
41 | For an example, it is possible to poison 'getline' by: | ||
42 | - adding a call to gl_WARN_ON_USE_PREPARE([[#include <stdio.h>]], | ||
43 | [getline]) in configure.ac, which potentially defines | ||
44 | HAVE_RAW_DECL_GETLINE | ||
45 | - adding this code to a header that wraps the system <stdio.h>: | ||
46 | #undef getline | ||
47 | #if HAVE_RAW_DECL_GETLINE | ||
48 | _GL_WARN_ON_USE (getline, "getline is required by POSIX 2008, but" | ||
49 | "not universally present; use the gnulib module getline"); | ||
50 | #endif | ||
51 | |||
52 | It is not possible to directly poison global variables. But it is | ||
53 | possible to write a wrapper accessor function, and poison that | ||
54 | (less common usage, like &environ, will cause a compilation error | ||
55 | rather than issue the nice warning, but the end result of informing | ||
56 | the developer about their portability problem is still achieved): | ||
57 | #if HAVE_RAW_DECL_ENVIRON | ||
58 | static char ***rpl_environ (void) { return &environ; } | ||
59 | _GL_WARN_ON_USE (rpl_environ, "environ is not always properly declared"); | ||
60 | # undef environ | ||
61 | # define environ (*rpl_environ ()) | ||
62 | #endif | ||
63 | */ | ||
64 | #ifndef _GL_WARN_ON_USE | ||
65 | |||
66 | # if 4 < __GNUC__ || (__GNUC__ == 4 && 3 <= __GNUC_MINOR__) | ||
67 | /* A compiler attribute is available in gcc versions 4.3.0 and later. */ | ||
68 | # define _GL_WARN_ON_USE(function, message) \ | ||
69 | extern __typeof__ (function) function __attribute__ ((__warning__ (message))) | ||
70 | # elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING | ||
71 | /* Verify the existence of the function. */ | ||
72 | # define _GL_WARN_ON_USE(function, message) \ | ||
73 | extern __typeof__ (function) function | ||
74 | # else /* Unsupported. */ | ||
75 | # define _GL_WARN_ON_USE(function, message) \ | ||
76 | _GL_WARN_EXTERN_C int _gl_warn_on_use | ||
77 | # endif | ||
78 | #endif | ||
79 | |||
80 | /* _GL_WARN_ON_USE_CXX (function, rettype, parameters_and_attributes, "string") | ||
81 | is like _GL_WARN_ON_USE (function, "string"), except that the function is | ||
82 | declared with the given prototype, consisting of return type, parameters, | ||
83 | and attributes. | ||
84 | This variant is useful for overloaded functions in C++. _GL_WARN_ON_USE does | ||
85 | not work in this case. */ | ||
86 | #ifndef _GL_WARN_ON_USE_CXX | ||
87 | # if 4 < __GNUC__ || (__GNUC__ == 4 && 3 <= __GNUC_MINOR__) | ||
88 | # define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \ | ||
89 | extern rettype function parameters_and_attributes \ | ||
90 | __attribute__ ((__warning__ (msg))) | ||
91 | # elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING | ||
92 | /* Verify the existence of the function. */ | ||
93 | # define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \ | ||
94 | extern rettype function parameters_and_attributes | ||
95 | # else /* Unsupported. */ | ||
96 | # define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \ | ||
97 | _GL_WARN_EXTERN_C int _gl_warn_on_use | ||
98 | # endif | ||
99 | #endif | ||
100 | |||
101 | /* _GL_WARN_EXTERN_C declaration; | ||
102 | performs the declaration with C linkage. */ | ||
103 | #ifndef _GL_WARN_EXTERN_C | ||
104 | # if defined __cplusplus | ||
105 | # define _GL_WARN_EXTERN_C extern "C" | ||
106 | # else | ||
107 | # define _GL_WARN_EXTERN_C extern | ||
108 | # endif | ||
109 | #endif | ||