Issue google#110 - Fix afl-clang-fast -E and -shared regressions.

llvm_mode/afl-clang-fast.c

@@ -103,7 +103,8 @@ static void find_obj(u8* argv0) {
 
 static void edit_params(u32 argc, char** argv) {
 
-  u8 fortify_set = 0, asan_set = 0, x_set = 0, bit_mode = 0;
+  u8 fortify_set = 0, asan_set = 0, x_set = 0, bit_mode = 0,
+     shared_linking = 0, preprocessor_only = 0;
   u8 *name;
 
   cc_params = ck_alloc((argc + 128) * sizeof(u8*));
@@ -158,6 +159,9 @@ static void edit_params(u32 argc, char** argv) {
     if (!strcmp(cur, "-Wl,-z,defs") ||
         !strcmp(cur, "-Wl,--no-undefined")) continue;
 
+    if (!strcmp(cur, "-E")) preprocessor_only = 1;
+    if (!strcmp(cur, "-shared")) shared_linking = 1;
+
     cc_params[cc_par_cnt++] = cur;
 
   }
@@ -277,6 +281,23 @@ static void edit_params(u32 argc, char** argv) {
     cc_params[cc_par_cnt++] = "none";
   }
 
+  if (preprocessor_only || shared_linking) {
+    /* In the preprocessor_only case (-E), we are not actually compiling at
+       all but requesting the compiler to output preprocessed sources only.
+       We must not add the runtime in this case because the compiler will
+       simply output its binary content back on stdout, breaking any build
+       systems that rely on a separate source preprocessing step.
+
+       The shared_linking case (-shared) is more complex. This flag should
+       only be passed when linking a shared object. When loading such a shared
+       object into a binary that has also been built with AFL, two AFL runtimes
+       will exist side-by-side. This is only a problem in the dynamic loading
+       case because for static linking, the compiler can de-duplicate the
+       runtime. We must hence avoid attaching the runtime to shared objects. */
+    cc_params[cc_par_cnt] = NULL;
+    return;
+  }
+
 #ifndef __ANDROID__
   switch (bit_mode) {