add AFL_NOOPT

README.md

@@ -399,10 +399,19 @@ How to do this is described below.
 
 Then build the target. (Usually with `make`)
 
-**NOTE**: sometimes configure and build systems are fickle and do not like
-stderr output (and think this means a test failure) - which is something
-afl++ like to do to show statistics. It is recommended to disable them via
-`export AFL_QUIET=1`.
+**NOTES**
+
+1. sometimes configure and build systems are fickle and do not like
+   stderr output (and think this means a test failure) - which is something
+   afl++ like to do to show statistics. It is recommended to disable them via
+   `export AFL_QUIET=1`.
+
+2. sometimes configure and build systems error on warnings - these should be
+   disabled (e.g. `--disable-werror` for some configure scripts`
+
+3. in case the configure/build system complains about afl++'s compiler and
+   aborts then set `export AFL_NOOPT=1` which will then just behave like the
+   real compiler. This option has to be unset again before building the target!
 
 ##### configure
 

docs/env_variables.md

@@ -26,6 +26,17 @@ Because (with the exception of the --afl-MODE command line option) the
 compile-time tools do not accept afl specific command-line options, they
 make fairly broad use of environmental variables instead:
 
+  - Some build/configure scripts break with afl++ compilers. To be able to
+    pass them, do:
+```
+       export CC=afl-cc
+       export CXX=afl-c++
+       export AFL_NOOPT=1
+       ./configure --disable-shared --disabler-werror
+       unset AFL_NOOPT
+       make
+```
+
   - Most afl tools do not print any output if stdout/stderr are redirected.
     If you want to get the output into a file then set the `AFL_DEBUG`
     environment variable.

include/envs.h

@@ -119,10 +119,12 @@ static char *afl_environment_variables[] = {
     "AFL_NO_PYTHON",
     "AFL_UNTRACER_FILE",
     "AFL_LLVM_USE_TRACE_PC",
-    "AFL_NO_X86",  // not really an env but we dont want to warn on it
     "AFL_MAP_SIZE",
     "AFL_MAPSIZE",
     "AFL_MAX_DET_EXTRAS",
+    "AFL_NO_X86",  // not really an env but we dont want to warn on it
+    "AFL_NOOPT",
+    "AFL_PASSTHROUGH",
     "AFL_PATH",
     "AFL_PERFORMANCE_FILE",
     "AFL_PRELOAD",

src/afl-cc.c

@@ -1025,7 +1025,7 @@ static void edit_params(u32 argc, char **argv, char **envp) {
 
 int main(int argc, char **argv, char **envp) {
 
-  int   i;
+  int   i, passthrough = 0;
   char *callname = argv[0], *ptr = NULL;
 
   if (getenv("AFL_DEBUG")) {
@@ -1045,6 +1045,13 @@ int main(int argc, char **argv, char **envp) {
 
   }
 
+  if (getenv("AFL_PASSTHROUGH") || getenv("AFL_NOOPT")) {
+
+    passthrough = 1;
+    if (!debug) { be_quiet = 1; }
+
+  }
+
   if ((ptr = strrchr(callname, '/')) != NULL) callname = ptr + 1;
   argvnull = (u8 *)argv[0];
   check_environment_vars(envp);
@@ -1665,6 +1672,7 @@ int main(int argc, char **argv, char **envp) {
           "  AFL_DONT_OPTIMIZE: disable optimization instead of -O3\n"
           "  AFL_NO_BUILTIN: no builtins for string compare functions (for "
           "libtokencap.so)\n"
+          "  AFL_NOOP: behave lik a normal compiler (to pass configure tests)\n"
           "  AFL_PATH: path to instrumenting pass and runtime  "
           "(afl-compiler-rt.*o)\n"
           "  AFL_IGNORE_UNKNOWN_ENVS: don't warn on unknown env vars\n"
@@ -1977,8 +1985,17 @@ int main(int argc, char **argv, char **envp) {
 
   }
 
+  if (passthrough) {
+
+    argv[0] = cc_params[0];
+    execvp(cc_params[0], (char **)argv);
+
+  } else {
+
     execvp(cc_params[0], (char **)cc_params);
 
+  }
+
   FATAL("Oops, failed to execute '%s' - check your PATH", cc_params[0]);
 
   return 0;

src/afl-common.c

@@ -682,6 +682,7 @@ void check_environment_vars(char **envp) {
             env[strlen(afl_environment_variables[i])] == '=') {
 
           match = 1;
+
           if ((val = getenv(afl_environment_variables[i])) && !*val) {
 
             WARNF(