configure: Be more verbose when compiler sanity checks fail

When configure could not get past initial compiler sanity check
the user was left with no explanation why this happened (usually
the reason is that compilers are not installed).

By printing the executed command line and re-executing it without
output redirection user gets better information how to proceed
(or ask for help) to resolve this problem.

The shell builtin 'printf' is used to print the executed command
line to ensure verbatim output.

diff --git a/configure b/configure
index 3447d868a552965ceed58c30946e0908f1730286..ed7c22800530669ca88ef9ab5d6b7c4d71b7de0c 100755 (executable)
--- a/configure
+++ b/configure
@@ -322,22 +322,29 @@ errors=0
 printf "int main(void){return 0;}\n" > minimal.c
 
 printf "Sanity checking C compilation environment... "
-if ${CC} ${CFLAGS} ${CPPFLAGS} minimal.c ${LDFLAGS} -o minimal > /dev/null 2>&1
+test_cmdline="${CC} ${CFLAGS} ${CPPFLAGS} minimal.c ${LDFLAGS} -o minimal"
+if  ${test_cmdline} > /dev/null 2>&1
 then
     printf "OK.\n"
 else
     printf "Fail.\n"
     errors=$((errors + 1))
+    printf Executed:; printf ' %s' ${test_cmdline}; echo
+    ${test_cmdline}
 fi
 
 printf "Sanity checking C++ compilation environment... "
-if ${CXX} ${CXXFLAGS_for_sh} ${CPPFLAGS} minimal.c ${LDFLAGS} -o minimal > /dev/null 2>&1
+test_cmdline="${CXX} ${CXXFLAGS_for_sh} ${CPPFLAGS} minimal.c ${LDFLAGS} -o minimal"
+if ${test_cmdline} > /dev/null 2>&1
 then
     printf "OK.\n"
 else
     printf "Fail.\n"
     errors=$((errors + 1))
+    printf Executed:; printf ' %s' ${test_cmdline}; echo
+    ${test_cmdline}
 fi
+unset test_cmdline
 
 if [ $errors -gt 0 ]; then
     cat <<EOF