enable errors on implicit functions by default; fixes #2175

5 files changed, 26 insertions, 14 deletions

diff --git a/tests/cubegeom_color.c b/tests/cubegeom_color.c
index 0d2b6ecb..7a41c64d 100644
--- a/tests/cubegeom_color.c
+++ b/tests/cubegeom_color.c
@@ -38,10 +38,6 @@ void verify() {
   for (int x = 0; x < width*height*4; x++) {
     if (x % 4 != 3) sum += x * data[x];
   }
-#ifdef __EMSCRIPTEN__
-  int result = sum;
-  REPORT_RESULT();
-#endif
 }
 
 int main(int argc, char *argv[])
diff --git a/tests/full_es2_sdlproc.c b/tests/full_es2_sdlproc.c
index d9ac072b..3f72f2bf 100644
--- a/tests/full_es2_sdlproc.c
+++ b/tests/full_es2_sdlproc.c
@@ -704,6 +704,8 @@ gears_init(void)
    gear3 = create_gear(1.3, 2.0, 0.5, 10, 0.7);
 }
 
+#include "SDL/SDL.h"
+
 int
 main(int argc, char *argv[])
 {
diff --git a/tests/sdl_headless.c b/tests/sdl_headless.c
index 6157a46d..e1836777 100644
--- a/tests/sdl_headless.c
+++ b/tests/sdl_headless.c
@@ -57,9 +57,6 @@ int main(int argc, char **argv) {
 
   printf("done.\n");
 
-  int result = sum > 3000 && sum < 5000; // varies a little on different browsers, font differences?
-  REPORT_RESULT();
-
   return 0;
 }
 
diff --git a/tests/test_other.py b/tests/test_other.py
index e381e1b3..2fecf09e 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -2521,16 +2521,24 @@ int main()
 }
 ''')
 
+    IMPLICIT_WARNING = '''warning: implicit declaration of function 'strnlen' is invalid in C99'''
+    IMPLICIT_ERROR = '''error: implicit declaration of function 'strnlen' is invalid in C99'''
+
     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'], []),
-      (['-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.
+      ([], None, [IMPLICIT_ERROR]),
+      (['-Wno-error=implicit-function-declaration'], ['abort()', 'it is worth building your source files with -Werror (warnings are errors), as warnings can indicate undefined behavior which can cause this'], [IMPLICIT_WARNING]), # turn error into warning
+      (['-Wno-implicit-function-declaration'], ['abort()', 'it is worth building your source files with -Werror (warnings are errors), as warnings can indicate undefined behavior which can cause this'], []), # turn error into nothing at all
+      (['-Wno-error=implicit-function-declaration', '-s', 'ASSERTIONS=2'], ['abort()', 'This pointer might make sense in another type signature'], []),
+      (['-Wno-error=implicit-function-declaration', '-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''']:
+      for ce in compile_expected + ['''warning: incompatible pointer types''']:
         self.assertContained(ce, stderr)
+      if expected is None:
+        assert not os.path.exists('a.out.js')
+      else:
+        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)
 
diff --git a/tools/shared.py b/tools/shared.py
index 31f0aad9..533906c9 100644
--- a/tools/shared.py
+++ b/tools/shared.py
@@ -662,6 +662,15 @@ if LLVM_TARGET != 'asmjs-unknown-emscripten':
   COMPILER_OPTS += ['-DEMSCRIPTEN', '-D__EMSCRIPTEN__', '-fno-math-errno',
                     '-U__native_client__', '-U__pnacl__', '-U__ELF__']
 
+# Changes to default clang behavior
+if LLVM_TARGET == 'asmjs-unknown-emscripten' or LLVM_TARGET == 'le32-unknown-nacl':
+  # Implicit functions can cause horribly confusing asm.js function pointer type errors, see #2175
+  # If your codebase really needs them - very unrecommended! - you can disable the error with
+  #   -Wno-error=implicit-function-declaration
+  # or disable even a warning about it with
+  #   -Wno-implicit-function-declaration
+  COMPILER_OPTS += ['-Werror=implicit-function-declaration']
+
 USE_EMSDK = not os.environ.get('EMMAKEN_NO_SDK')
 
 if USE_EMSDK: