diff options
Diffstat (limited to 'm4/gnulib-common.m4')
| -rw-r--r-- | m4/gnulib-common.m4 | 87 |
1 files changed, 76 insertions, 11 deletions
diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4 index 2b253da..6c4cad6 100644 --- a/m4/gnulib-common.m4 +++ b/m4/gnulib-common.m4 @@ -1,5 +1,5 @@ -# gnulib-common.m4 serial 41 -dnl Copyright (C) 2007-2018 Free Software Foundation, Inc. +# gnulib-common.m4 serial 46 +dnl Copyright (C) 2007-2020 Free Software Foundation, Inc. dnl This file is free software; the Free Software Foundation dnl gives unlimited permission to copy and/or distribute it, dnl with or without modifications, as long as this notice is preserved. @@ -17,10 +17,20 @@ AC_DEFUN([gl_COMMON_BODY], [ AH_VERBATIM([_Noreturn], [/* The _Noreturn keyword of C11. */ #ifndef _Noreturn -# if 201103 <= (defined __cplusplus ? __cplusplus : 0) +# if (defined __cplusplus \ + && ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \ + || (defined _MSC_VER && 1900 <= _MSC_VER)) \ + && 0) + /* [[noreturn]] is not practically usable, because with it the syntax + extern _Noreturn void func (...); + would not be valid; such a declaration would only be valid with 'extern' + and '_Noreturn' swapped, or without the 'extern' keyword. However, some + AIX system header files and several gnulib header files use precisely + this syntax with 'extern'. */ # define _Noreturn [[noreturn]] -# elif (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \ - || 4 < __GNUC__ + (7 <= __GNUC_MINOR__)) +# elif ((!defined __cplusplus || defined __clang__) \ + && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \ + || 4 < __GNUC__ + (7 <= __GNUC_MINOR__))) /* _Noreturn works as-is. */ # elif 2 < __GNUC__ + (8 <= __GNUC_MINOR__) || 0x5110 <= __SUNPRO_C # define _Noreturn __attribute__ ((__noreturn__)) @@ -85,6 +95,60 @@ AC_DEFUN([gl_COMMON_BODY], [ # define _GL_ATTRIBUTE_MALLOC /* empty */ #endif ]) + AH_VERBATIM([async_safe], +[/* The _GL_ASYNC_SAFE marker should be attached to functions that are + signal handlers (for signals other than SIGABRT, SIGPIPE) or can be + invoked from such signal handlers. Such functions have some restrictions: + * All functions that it calls should be marked _GL_ASYNC_SAFE as well, + or should be listed as async-signal-safe in POSIX + <https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04> + section 2.4.3. Note that malloc(), sprintf(), and fwrite(), in + particular, are NOT async-signal-safe. + * All memory locations (variables and struct fields) that these functions + access must be marked 'volatile'. This holds for both read and write + accesses. Otherwise the compiler might optimize away stores to and + reads from such locations that occur in the program, depending on its + data flow analysis. For example, when the program contains a loop + that is intended to inspect a variable set from within a signal handler + while (!signal_occurred) + ; + the compiler is allowed to transform this into an endless loop if the + variable 'signal_occurred' is not declared 'volatile'. + Additionally, recall that: + * A signal handler should not modify errno (except if it is a handler + for a fatal signal and ends by raising the same signal again, thus + provoking the termination of the process). If it invokes a function + that may clobber errno, it needs to save and restore the value of + errno. */ +#define _GL_ASYNC_SAFE +]) + dnl Hint which direction to take regarding cross-compilation guesses: + dnl When a user installs a program on a platform they are not intimately + dnl familiar with, --enable-cross-guesses=conservative is the appropriate + dnl choice. It implements the "If we don't know, assume the worst" principle. + dnl However, when an operating system developer (on a platform which is not + dnl yet known to gnulib) builds packages for their platform, they want to + dnl expose, not hide, possible platform bugs; in this case, + dnl --enable-cross-guesses=risky is the appropriate choice. + dnl Sets the variables + dnl gl_cross_guess_normal (to be used when 'yes' is good and 'no' is bad), + dnl gl_cross_guess_inverted (to be used when 'no' is good and 'yes' is bad). + AC_ARG_ENABLE([cross-guesses], + [AS_HELP_STRING([--enable-cross-guesses={conservative|risky}], + [specify policy for cross-compilation guesses])], + [if test "x$enableval" != xconservative && test "x$enableval" != xrisky; then + AC_MSG_WARN([invalid argument supplied to --enable-cross-guesses]) + enableval=conservative + fi + gl_cross_guesses="$enableval"], + [gl_cross_guesses=conservative]) + if test $gl_cross_guesses = risky; then + gl_cross_guess_normal="guessing yes" + gl_cross_guess_inverted="guessing no" + else + gl_cross_guess_normal="guessing no" + gl_cross_guess_inverted="guessing yes" + fi dnl Preparation for running test programs: dnl Tell glibc to write diagnostics from -D_FORTIFY_SOURCE=2 to stderr, not dnl to /dev/tty, so they can be redirected to log files. Such diagnostics @@ -351,12 +415,13 @@ AC_DEFUN([AC_C_RESTRICT], nothing if this is not supported. Do not define if restrict is supported directly. */ #undef restrict -/* Work around a bug in Sun C++: it does not support _Restrict or - __restrict__, even though the corresponding Sun C compiler ends up with - "#define restrict _Restrict" or "#define restrict __restrict__" in the - previous line. Perhaps some future version of Sun C++ will work with - restrict; if so, hopefully it defines __RESTRICT like Sun C does. */ -#if defined __SUNPRO_CC && !defined __RESTRICT +/* Work around a bug in older versions of Sun C++, which did not + #define __restrict__ or support _Restrict or __restrict__ + even though the corresponding Sun C compiler ended up with + "#define restrict _Restrict" or "#define restrict __restrict__" + in the previous line. This workaround can be removed once + we assume Oracle Developer Studio 12.5 (2016) or later. */ +#if defined __SUNPRO_CC && !defined __RESTRICT && !defined __restrict__ # define _Restrict # define __restrict__ #endif]) |