include/libc-diag.h

   1 /* Macros for controlling diagnostic output from the compiler.
   2    Copyright (C) 2014-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _LIBC_DIAG_H
  20 #define _LIBC_DIAG_H 1
  21
  22 /* Ignore the value of an expression when a cast to void does not
  23    suffice (in particular, for a call to a function declared with
  24    attribute warn_unused_result).  */
  25 #define ignore_value(x) \
  26   ({ __typeof__ (x) __ignored_value = (x); (void) __ignored_value; })
  27
  28 /* The macros to control diagnostics are structured like this, rather
  29    than a single macro that both pushes and pops diagnostic state and
  30    takes the affected code as an argument, because the GCC pragmas
  31    work by disabling the diagnostic for a range of source locations
  32    and do not work when all the pragmas and the affected code are in a
  33    single macro expansion.  */
  34
  35 /* Push diagnostic state.  */
  36 #define DIAG_PUSH_NEEDS_COMMENT _Pragma ("GCC diagnostic push")
  37
  38 /* Pop diagnostic state.  */
  39 #define DIAG_POP_NEEDS_COMMENT _Pragma ("GCC diagnostic pop")
  40
  41 #define _DIAG_STR1(s) #s
  42 #define _DIAG_STR(s) _DIAG_STR1(s)
  43
  44 /* Ignore the diagnostic OPTION.  VERSION is the most recent GCC
  45    version for which the diagnostic has been confirmed to appear in
  46    the absence of the pragma (in the form MAJOR.MINOR for GCC 4.x,
  47    just MAJOR for GCC 5 and later).  Uses of this pragma should be
  48    reviewed when the GCC version given is no longer supported for
  49    building glibc; the version number should always be on the same
  50    source line as the macro name, so such uses can be found with grep.
  51    Uses should come with a comment giving more details of the
  52    diagnostic, and an architecture on which it is seen if possibly
  53    optimization-related and not in architecture-specific code.  This
  54    macro should only be used if the diagnostic seems hard to fix (for
  55    example, optimization-related false positives).  */
  56 #define DIAG_IGNORE_NEEDS_COMMENT(version, option)     \
  57   _Pragma (_DIAG_STR (GCC diagnostic ignored option))
  58
  59 /* Similar to DIAG_IGNORE_NEEDS_COMMENT the following macro ignores the
  60    diagnostic OPTION but only if optimizations for size are enabled.
  61    This is required because different warnings may be generated for
  62    different optimization levels.  For example a key piece of code may
  63    only generate a warning when compiled at -Os, but at -O2 you could
  64    still want the warning to be enabled to catch errors.  In this case
  65    you would use DIAG_IGNORE_Os_NEEDS_COMMENT to disable the warning
  66    only for -Os.  */
  67 #ifdef __OPTIMIZE_SIZE__
  68 # define DIAG_IGNORE_Os_NEEDS_COMMENT(version, option) \
  69   _Pragma (_DIAG_STR (GCC diagnostic ignored option))
  70 #else
  71 # define DIAG_IGNORE_Os_NEEDS_COMMENT(version, option)
  72 #endif
  73
  74 #endif /* libc-diag.h */