fail when clang -### <args> returns nothing

Summary:
Since clang -### can silently return nothing when passed bogus arguments (eg,
trying to compile a non-existent file), run the original command in that case
in case it's a genuine error. This prevents puzzling behaviours such as
`infer -- clang -c bogus_file.c` succeeding with 0 files analyzed.

Reviewed By: martinoluca

Differential Revision: D3592924

fbshipit-source-id: 5d8bc81

infer/lib/clang_wrappers/hijack_and_normalize_clang_command.sh

@@ -54,7 +54,17 @@ else
         sed -e 's#^\(^clang: error:.*$\)#echo "\1"; exit 1#g' | \
         # add trailing ; to each line
         sed -e 's/$/;/g')
-    eval $CC_COMMAND
+    if [ -n "$CC_COMMAND" ]; then
+        eval $CC_COMMAND
+    else
+        # No command to execute after -###, this is fishy, let's execute the original command
+        # instead.
+        #
+        # In particular, this can happen when the user tries to run `infer -- clang -c
+        # file_that_does_not_exist.c`. In this case, this will fail with the appropriate error
+        # message from clang instead of silently analyzing 0 files.
+        "$CLANG_COMPILER$XX" "$@"
+    fi
     STATUS=$?
 fi