configure: work around compilers that merely warn for unknown options
some compilers (such as clang) accept unknown options without error,
but then print warnings on each invocation, cluttering the build
output and burying meaningful warnings. this patch makes configure's
tryflag and tryldflag functions use additional options to turn the
unknown-option warnings into errors, if available, but only at check
time. these options are not output in config.mak to avoid the risk of
spurious build breakage; if they work, they will have already done
their job at configure time.
diff --git a/configure b/configure
index 143dc92..7b29ae4 100755
--- a/configure
+++ b/configure
@@ -80,7 +80,7 @@
tryflag () {
printf "checking whether compiler accepts %s... " "$2"
echo "typedef int x;" > "$tmpc"
-if $CC $2 -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
+if $CC $CFLAGS_TRY $2 -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
printf "yes\n"
eval "$1=\"\${$1} \$2\""
eval "$1=\${$1# }"
@@ -94,7 +94,7 @@
tryldflag () {
printf "checking whether linker accepts %s... " "$2"
echo "typedef int x;" > "$tmpc"
-if $CC -nostdlib -shared "$2" -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
+if $CC $LDFLAGS_TRY -nostdlib -shared "$2" -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
printf "yes\n"
eval "$1=\"\${$1} \$2\""
eval "$1=\${$1# }"
@@ -113,7 +113,9 @@
CFLAGS_AUTO=
CFLAGS_MEMOPS=
CFLAGS_NOSSP=
+CFLAGS_TRY=
LDFLAGS_AUTO=
+LDFLAGS_TRY=
OPTIMIZE_GLOBS=
prefix=/usr/local/musl
exec_prefix='$(prefix)'
@@ -205,6 +207,14 @@
fi
#
+# Figure out options to force errors on unknown flags.
+#
+tryflag CFLAGS_TRY -Werror=unknown-warning-option
+tryflag CFLAGS_TRY -Werror=unused-command-line-argument
+tryldflag LDFLAGS_TRY -Werror=unknown-warning-option
+tryldflag LDFLAGS_TRY -Werror=unused-command-line-argument
+
+#
# Need to know if the compiler is gcc to decide whether to build the
# musl-gcc wrapper, and for critical bug detection in some gcc versions.
#