Define behavior that 'emcc -c a.c -o dir/' shall compile and generate object file 'dir/a.o'. Previous behavior when directory was specified in -o was accidental, and it generated an object file 'dir/a_0.o'. Add new command line option --default-obj-ext that allows specifying the file suffix that is used when the output object filename is generated in this manner. '.o' is a good default suffix since it parallels the existing gcc/clang/linux convention. For Windows Visual Studio+CMake+Emscripten integration, CMake has been hardcoded to assume that if Visual Studio is targeted, the compiler will always generate '.obj' files. Hence having the ability to adjust the default naming scheme with --default-obj-ext enables working around CMake inflexibility, and add support for CMake+VS+Emscripten triple.

2 files changed, 33 insertions, 1 deletions

diff --git a/emcc b/emcc
index 111093e2..8f98c3cd 100755
--- a/emcc
+++ b/emcc
@@ -517,6 +517,13 @@ Options that are modified or new in %s include:
                            file, and if that is not set, the default location
                            ~/.emscripten is assumed.
 
+  --default-obj-ext .ext   Specifies the file suffix to generate if the location
+                           of a directory name is passed to -o directive, e.g.
+                             emcc -c a.c -o dir/
+                           will by default generate an output name 'dir/a.o', 
+                           but this cmdline param can be passed to generate a
+                           file with a custom suffix 'dir/a.ext'. 
+
 The target file, if specified (-o <target>), defines what will
 be generated:
 
@@ -804,6 +811,7 @@ try:
   use_preload_cache = False
   no_heap_copy = False
   proxy_to_worker = False
+  default_object_extension = '.o'
 
   if use_cxx:
     default_cxx_std = '-std=c++03' # Enforce a consistent C++ standard when compiling .cpp files, if user does not specify one on the cmdline.
@@ -999,6 +1007,12 @@ try:
       # This option is parsed in tools/shared.py, here only clean it up from being passed to clang.
       newargs[i] = ''
       newargs[i+1] = ''
+    elif newargs[i] == '--default-obj-ext':
+      newargs[i] = ''
+      default_object_extension = newargs[i+1]
+      if not default_object_extension.startswith('.'):
+        default_object_extension = '.' + default_object_extension
+      newargs[i+1] = ''
 
   newargs = [ arg for arg in newargs if arg is not '' ]
 
@@ -1340,7 +1354,16 @@ try:
     else:
       if len(input_files) == 1:
         temp_output_base = in_temp(unsuffixed(uniquename(input_files[0])))
-        shutil.move(temp_output_base + '.o', specified_target)
+        if specified_target.endswith('/') or specified_target.endswith('\\') or os.path.isdir(specified_target): # User passed '-o <directory' as the location to output to.
+          obj_output_name = os.path.join(specified_target, os.path.splitext(os.path.basename(input_file))[0] + default_object_extension)
+          logging.debug('User specified -o <directoryname> as the location of the output. Generating output file ' + obj_output_name)
+          try:
+            shutil.move(temp_output_base + '.o', obj_output_name)
+          except IOError, e:
+            logging.error('Could not write to output file ' + obj_output_name + '. Perhaps the output directory does not exist?')
+            exit(1)
+        else: # User passed '-o <filename>' as the location to output to.
+          shutil.move(temp_output_base + '.o', specified_target)
         if os.path.exists(temp_output_base + '.d'):
           # There was a .d file generated, from -MD or -MMD and friends, save a copy of it to where the output resides,
           # adjusting the target name away from the temporary file name to the specified target.
diff --git a/tests/test_other.py b/tests/test_other.py
index 0c325c74..eb9bd23d 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -2187,3 +2187,12 @@ mergeInto(LibraryManager.library, {
     out, err = process.communicate()
     assert process.returncode is 0, 'float.h should agree with our system: ' + out + '\n\n\n' + err
 
+  def test_default_obj_ext(self):
+    outdir = os.path.join(self.get_dir(), 'out_dir') + '/'
+    os.mkdir(outdir)
+    process = Popen([PYTHON, EMCC, '-c', path_from_root('tests', 'hello_world.c'), '-o', outdir], stdout=PIPE, stderr=PIPE)
+    process.communicate()
+    assert(os.path.isfile(outdir + 'hello_world.o'))
+    process = Popen([PYTHON, EMCC, '-c', path_from_root('tests', 'hello_world.c'), '-o', outdir, '--default-obj-ext', 'obj'], stdout=PIPE, stderr=PIPE)
+    process.communicate()
+    assert(os.path.isfile(outdir + 'hello_world.obj'))