Hi,
I relies on some compiler's check to reduce some simple coding issues, I use clang 18.1.6 for now. however "CFLAGS='-Wall -Werror ' ./configure" would fail, and if I run ' ./configure' directly, it is OK. I'm not sure why it happens. More details is below: (master)> echo $CC clang (master)> clang --version clang version 18.1.6 (https://gitee.com/mirrors/llvm-project.git 1118c2e05e67a36ed8ca250524525cdb66a55256) Target: x86_64-unknown-linux-gnu Thread model: posix InstalledDir: /usr/local/bin (master)> CFLAGS='-Wall -Werror ' ./configure checking for clang option to accept ISO C89... unsupported checking for clang option to accept ISO C99... unsupported configure: error: C compiler "clang" does not support C99 In config.log, we can see: configure:4433: clang -qlanglvl=extc89 -c -Wall -Werror conftest.c >&5 clang: error: unknown argument: '-qlanglvl=extc89' and clang does doesn't support -qlanglvl. in 'configure', we can see the related code is: """ for ac_arg in '' -std=gnu99 -std=c99 -c99 -AC99 -D_STDC_C99= -qlanglvl=extc99 do CC="$ac_save_CC $ac_arg" if ac_fn_c_try_compile "$LINENO"; then : ac_cv_prog_cc_c99=$ac_arg fi rm -f core conftest.err conftest.$ac_objext test "x$ac_cv_prog_cc_c99" != "xno" && break done rm -f conftest.$ac_ext CC=$ac_save_CC .... # Error out if the compiler does not support C99, as the codebase # relies on that. if test "$ac_cv_prog_cc_c99" = no; then as_fn_error $? "C compiler \"$CC\" does not support C99" "$LINENO" 5 fi """ So my questions are: 1. based on the fact clang doesn't support '-qlanglvl' all the time, why removing the CFLAGS matters. 2. If you are using clang as well, what CFLAGS you use and it works? for example: IIRC, clang doesn't report error when a variable is set but no used by default, we have to add some extra flags to make it. -- Best Regards Andy Fan
