configure: Add sanity checking for environment variables

Passing in environment variables incompatible with the compiler may
cause other parts of the configure script to fail in hard to
understand ways, so we abort early.

diff --git a/configure b/configure
index 4af7ba94f7bd344cba6fb9e355e10ae5034717a4..2065fcdf6f4ce3af7b5570b3092804027af68df9 100755 (executable)
--- a/configure
+++ b/configure
@@ -47,6 +47,7 @@ CC=${CC:-cc}
 CXX=${CXX:-c++}
 CFLAGS=${CFLAGS:--g -O2}
 CPPFLAGS=${CPPFLAGS:-}
+CXXFLAGS_for_sh=${CXXFLAGS:-${CFLAGS}}
 CXXFLAGS=${CXXFLAGS:-\$(CFLAGS)}
 LDFLAGS=${LDFLAGS:-}
 XAPIAN_CONFIG=${XAPIAN_CONFIG:-xapian-config}
@@ -269,6 +270,35 @@ dependencies are available:
 EOF
 
 errors=0
+printf "int main(void){return 0;}\n" > minimal.c
+
+printf "Sanity checking C compilation environment... "
+if ${CC} ${CFLAGS} ${CPPFLAGS} minimal.c ${LDFLAGS} -o minimal > /dev/null 2>&1
+then
+    printf "OK.\n"
+else
+    printf "Fail.\n"
+    errors=$((errors + 1))
+fi
+
+printf "Sanity checking C++ compilation environment... "
+if ${CXX} ${CXXFLAGS_for_sh} ${CPPFLAGS} minimal.c ${LDFLAGS} -o minimal > /dev/null 2>&1
+then
+    printf "OK.\n"
+else
+    printf "Fail.\n"
+    errors=$((errors + 1))
+fi
+
+if [ $errors -gt 0 ]; then
+    cat <<EOF
+*** Error: Initial sanity checking of environment failed.  Please try
+running configure in a clean environment, and if the problem persists,
+report a bug.
+EOF
+    rm -f minimal minimal.c
+    exit 1
+fi
 
 if pkg-config --version > /dev/null 2>&1; then
     have_pkg_config=1
@@ -690,8 +720,6 @@ else
 fi
 rm -f compat/check_asctime
 
-printf "int main(void){return 0;}\n" > minimal.c
-
 printf "Checking for rpath support... "
 if ${CC} -Wl,--enable-new-dtags -Wl,-rpath,/tmp/ -o minimal minimal.c >/dev/null 2>&1
 then