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Diffstat (limited to 'm4/cc-flags.m4')
| -rw-r--r-- | m4/cc-flags.m4 | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/m4/cc-flags.m4 b/m4/cc-flags.m4 new file mode 100644 index 0000000..8a5aa8a --- /dev/null +++ b/m4/cc-flags.m4 @@ -0,0 +1,112 @@ +dnl Check whether the compiler supports particular flags. +dnl +dnl Provides RRA_PROG_CC_FLAG, which checks whether a compiler supports a +dnl given flag. If it does, the commands in the second argument are run. If +dnl not, the commands in the third argument are run. +dnl +dnl Provides RRA_PROG_CC_WARNINGS_FLAGS, which checks whether a compiler +dnl supports a large set of warning flags and sets the WARNINGS_CFLAGS +dnl substitution variable to all of the supported warning flags. (Note that +dnl this may be too aggressive for some people.) +dnl +dnl Depends on RRA_PROG_CC_CLANG. +dnl +dnl The canonical version of this file is maintained in the rra-c-util +dnl package, available at <https://www.eyrie.org/~eagle/software/rra-c-util/>. +dnl +dnl Copyright 2016-2018 Russ Allbery <eagle@eyrie.org> +dnl Copyright 2006, 2009, 2016 +dnl by Internet Systems Consortium, Inc. ("ISC") +dnl +dnl Permission to use, copy, modify, and/or distribute this software for any +dnl purpose with or without fee is hereby granted, provided that the above +dnl copyright notice and this permission notice appear in all copies. +dnl +dnl THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH +dnl REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF +dnl MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY +dnl SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES +dnl WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN +dnl ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR +dnl IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +dnl +dnl SPDX-License-Identifier: ISC + +dnl Used to build the result cache name. +AC_DEFUN([_RRA_PROG_CC_FLAG_CACHE], +[translit([rra_cv_compiler_c_$1], [-=+], [___])]) + +dnl Check whether a given flag is supported by the complier. +AC_DEFUN([RRA_PROG_CC_FLAG], +[AC_REQUIRE([AC_PROG_CC]) + AC_MSG_CHECKING([if $CC supports $1]) + AC_CACHE_VAL([_RRA_PROG_CC_FLAG_CACHE([$1])], + [save_CFLAGS=$CFLAGS + AS_CASE([$1], + [-Wno-*], [CFLAGS="$CFLAGS `echo "$1" | sed 's/-Wno-/-W/'`"], + [*], [CFLAGS="$CFLAGS $1"]) + AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [int foo = 0;])], + [_RRA_PROG_CC_FLAG_CACHE([$1])=yes], + [_RRA_PROG_CC_FLAG_CACHE([$1])=no]) + CFLAGS=$save_CFLAGS]) + AC_MSG_RESULT([$_RRA_PROG_CC_FLAG_CACHE([$1])]) + AS_IF([test x"$_RRA_PROG_CC_FLAG_CACHE([$1])" = xyes], [$2], [$3])]) + +dnl Determine the full set of viable warning flags for the current compiler. +dnl +dnl This is based partly on personal preference and is a fairly aggressive set +dnl of warnings. Desirable CC warnings that can't be turned on due to other +dnl problems: +dnl +dnl -Wsign-conversion Too many fiddly changes for the benefit +dnl -Wstack-protector Too many false positives from small buffers +dnl +dnl Last checked against gcc 7.2.0 (2017-12-28). -D_FORTIFY_SOURCE=2 enables +dnl warn_unused_result attribute markings on glibc functions on Linux, which +dnl catches a few more issues. Add -O2 because gcc won't find some warnings +dnl without optimization turned on. +dnl +dnl For Clang, we try to use -Weverything, but we have to disable some of the +dnl warnings: +dnl +dnl -Wcast-qual Some structs require casting away const +dnl -Wdisabled-macro-expansion Triggers on libc (sigaction.sa_handler) +dnl -Wpadded Not an actual problem +dnl -Wreserved-id-macros Autoconf sets several of these normally +dnl -Wsign-conversion Too many fiddly changes for the benefit +dnl -Wtautological-pointer-compare False positives with for loops +dnl -Wundef Conflicts with Autoconf probe results +dnl -Wunreachable-code Happens with optional compilation +dnl -Wunreachable-code-return Other compilers get confused +dnl -Wunused-macros Often used on suppressed branches +dnl -Wused-but-marked-unused Happens a lot with conditional code +dnl +dnl Sets WARNINGS_CFLAGS as a substitution variable. +AC_DEFUN([RRA_PROG_CC_WARNINGS_FLAGS], +[AC_REQUIRE([RRA_PROG_CC_CLANG]) + AS_IF([test x"$CLANG" = xyes], + [WARNINGS_CFLAGS="-Werror" + m4_foreach_w([flag], + [-Weverything -Wno-cast-qual -Wno-disabled-macro-expansion -Wno-padded + -Wno-sign-conversion -Wno-reserved-id-macro + -Wno-tautological-pointer-compare -Wno-undef -Wno-unreachable-code + -Wno-unreachable-code-return -Wno-unused-macros + -Wno-used-but-marked-unused], + [RRA_PROG_CC_FLAG(flag, + [WARNINGS_CFLAGS="${WARNINGS_CFLAGS} flag"])])], + [WARNINGS_CFLAGS="-g -O2 -D_FORTIFY_SOURCE=2 -Werror" + m4_foreach_w([flag], + [-fstrict-overflow -fstrict-aliasing -Wall -Wextra -Wformat=2 + -Wformat-overflow=2 -Wformat-signedness -Wformat-truncation=2 + -Wnull-dereference -Winit-self -Wswitch-enum -Wstrict-overflow=5 + -Wmissing-format-attribute -Walloc-zero -Wduplicated-branches + -Wduplicated-cond -Wtrampolines -Wfloat-equal + -Wdeclaration-after-statement -Wshadow -Wpointer-arith + -Wbad-function-cast -Wcast-align -Wwrite-strings -Wconversion + -Wno-sign-conversion -Wdate-time -Wjump-misses-init -Wlogical-op + -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes + -Wmissing-declarations -Wnormalized=nfc -Wpacked -Wredundant-decls + -Wrestrict -Wnested-externs -Winline -Wvla], + [RRA_PROG_CC_FLAG(flag, + [WARNINGS_CFLAGS="${WARNINGS_CFLAGS} flag"])])]) + AC_SUBST([WARNINGS_CFLAGS])]) |