add test for #2175

2 files changed, 27 insertions, 0 deletions

diff --git a/emscripten.py b/emscripten.py
index eeb53bf7..26c7d6ef 100755
--- a/emscripten.py
+++ b/emscripten.py
@@ -780,6 +780,8 @@ def emscript_fast(infile, settings, outfile, libraries=[], compiler_engine=None,
   table_sizes = {}
   for k, v in metadata['tables'].iteritems():
     table_sizes[k] = str(v.count(',')) # undercounts by one, but that is what we want
+    #if settings['ASSERTIONS'] >= 2 and table_sizes[k] == 0:
+    #  print >> sys.stderr, 'warning: no function pointers with signature ' + k + ', but there is a call, which will abort if it occurs (this can result from undefined behavior, check for compiler warnings on your source files and consider -Werror)'
   funcs = re.sub(r"#FM_(\w+)#", lambda m: table_sizes[m.groups(0)[0]], funcs)
 
   # fix +float into float.0, if not running js opts
diff --git a/tests/test_other.py b/tests/test_other.py
index 18a64c85..5959e56d 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -2509,3 +2509,28 @@ Waste<3> *getMore() {
       self.assertContained('argc: 1\n16\n17\n10\n', run_js('a.out.js'))
       assert ('_GLOBAL_' in src) == has_global
 
+  def test_implicit_func(self):
+    open('src.c', 'w').write(r'''
+#include <stdio.h>
+int main()
+{
+    printf("hello %d\n", strnlen("waka", 2)); // Implicit declaration, no header, for strnlen
+    int (*my_strnlen)(char*, ...) = strnlen;
+    printf("hello %d\n", my_strnlen("shaka", 2));
+    return 0;
+}
+''')
+
+    for opts, expected, compile_expected in [
+      ([], ['abort()', 'it is worth building your source files with -Werror (warnings are errors), as warnings can indicate undefined behavior which can cause this'], []),
+      (['-s', 'ASSERTIONS=2'], ['abort()', 'This pointer might make sense in another type signature: ii: _strnlen'], []),
+      (['-O1'], ['hello 2\nhello 5\n'], []), # invalid output - second arg is sent as varargs, but needs to be int. llvm optimizer avoided the crash silently, caused undefined behavior... at least people can debug this by running an -O0 build.
+    ]:
+      print opts, expected
+      stdout, stderr = Popen([PYTHON, EMCC, 'src.c'] + opts, stderr=PIPE).communicate()
+      output = run_js(os.path.join(self.get_dir(), 'a.out.js'), stderr=PIPE, full_output=True)
+      for e in expected:
+        self.assertContained(e, output)
+      for ce in compile_expected + ['''warning: implicit declaration of function 'strnlen' is invalid in C99''', '''warning: incompatible pointer types''']:
+        self.assertContained(ce, stderr)
+