build-sys: Perform flag tests in context to existing flags Fix the CC_CHECK_FLAG_APPEND macro to test appended flags in context to current flag values. Otherwise, it is possible to append flags colliding with user's *FLAGS or even previously appended flags that will cause the build to fail.

build-sys: Check behavior of -Werror=shadow before deciding to use it gcc versions 4.6 and earlier used to complain when a local variable shadows a global function, 4.7 and above only complain if a local variable shadows a global variable. Fix this by checking whether gcc 4.7+ behavior is in place before deciding to use -Werror=shadow in $(CFLAGS), by using a custom test program source that shadows a global function with a local variable and confirming that -Werror=shadow does not make the compile to break. Tested: - On gcc 4.7 and 4.8, confirmed nothing changed (other than the order of the -Werror=shadow argument, going to the end of CFLAGS.) - On gcc 4.6, confirmed by looking at the config.log output that the check for -Werror=shadow failed and it was not included in CFLAGS. - Ran `make V=1` to confirm -Werror=shadow was still in use, introduced a bogus shadowing issue and confirmed it was caught when building with a recent gcc.

build-sys: properly quote m4 macro arguments in CC_CHECK_FLAGS_APPEND The variables should be quoted inside [...] to avoid double macro expansion. This is currently not an issue, since the values (-W...) are not really macros, but we might as well just fix that issue now. Tested by re-running autogen.sh and comparing the value of OUR_CFLAGS in the generated Makefile. Ran a full build from a clean tree to confirm no other issues were introduced.

build: make sure to test for -Wflag instead of -Wno-flag gcc does not support testing for negated warnings. See here for details: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63499 This patch changes CC_CHECK_FLAG_APPEND to always test for the non-negated warnings.

s/commandline/command line/g

build-sys: fix conftest.c to work on arm All tests for compiler support were failing with: /usr/bin/ld: /tmp/ccwnVc2A.o: relocation R_ARM_MOVW_ABS_NC against `a' can not be used when making a shared object; recompile with -fPIC

build: check for build/link flags harder Use AC_LINK_IFELSE instead of AC_COMPILE_IFELSE to test for flags that might succeed during compilation but not during linking. An example is gcc compiled with libssp support but gnu-ld without it. In this case -fstack-protector works fine during compilation but fails during linking as several internal helpers are missing.

replace tabs with spaces in various files The affected files in this patch had inconsistent use of tabs vs. spaces for indentation, and this patch eliminates the stray tabs. Also, the opening brace of sigchld_hdl() in activate.c was moved so the opening braces are consistent throughout the file.

build-sys: Append -Werror when testing flags Clang don't treat unknown warnings flags as an error, but rather as a warning. The result is that the detection for whic CFLAGS are supported by this compiler will not work, since the compilation will succeed. With this patch we now successfully detect clang doesn't support -Wlogical-op, as opposed to previous behavior: checking if clang supports flag -Wlogical-op in envvar CFLAGS... no We use this macro only for LDFLAGS and CFLAGS, so it's safe to stash -Werror there.

build-sys: do not set CFLAGS directly Set a separate variable for adding warning flags. Build systems are not supposed to change CFLAGS and LDFLAGS, these are user variables. Reference: http://www.gnu.org/software/automake/manual/html_node/Flag-Variables-Ordering.html

build-sys: fix AC_COMPILE_IFELSE tests This removes some warnings when bootstrapping. The warnings were introduced in autoconf 2.68. Reference: http://www.flameeyes.eu/autotools-mythbuster/forwardporting/autoconf.html The following code AC_COMPILE_IFELSE([ <MY C CODE HERE> ], ...) is changed to AC_COMPILE_IFELSE( [AC_COMPILE_IFELSE([AC_LANG_SOURCE([ <MY C CODE HERE> ])], ...)

build: basic autoconfization

autoconfization