Support -gseparate-dwarf=FILENAME. fixes #10759 (#10766)

Author: kripken

emcc.py

@@ -2825,9 +2825,17 @@ def check_bad_eq(arg):
         if requested_level.startswith('force_dwarf'):
           exit_with_error('gforce_dwarf was a temporary option and is no longer necessary (use -g)')
         elif requested_level.startswith('separate-dwarf'):
-          # Emit full DWARF but also emit it in a file on the side
+          # emit full DWARF but also emit it in a file on the side
           newargs[i] = '-g'
-          shared.Settings.SEPARATE_DWARF = 1
+          # if a file is provided, use that; otherwise use the default location
+          # (note that we do not know the default location until all args have
+          # been parsed, so just note True for now).
+          if requested_level != 'separate-dwarf':
+            if not requested_level.startswith('separate-dwarf=') or requested_level.count('=') != 1:
+              exit_with_error('invalid -gseparate-dwarf=FILENAME notation')
+            shared.Settings.SEPARATE_DWARF = requested_level.split('=')[1]
+          else:
+            shared.Settings.SEPARATE_DWARF = True
         # a non-integer level can be something like -gline-tables-only. keep
         # the flag for the clang frontend to emit the appropriate DWARF info.
         # set the emscripten debug level to 3 so that we do not remove that
@@ -3317,7 +3325,11 @@ def run_closure_compiler(final):
     save_intermediate_with_wasm('symbolmap', wasm_binary_target)
 
   if shared.Settings.DEBUG_LEVEL >= 3 and shared.Settings.SEPARATE_DWARF and os.path.exists(wasm_binary_target):
-    shared.Building.emit_debug_on_side(wasm_binary_target)
+    # if the dwarf filename wasn't provided, use the default target + a suffix
+    dwarf_target = shared.Settings.SEPARATE_DWARF
+    if dwarf_target is True:
+      dwarf_target = wasm_binary_target + '.debug.wasm'
+    shared.Building.emit_debug_on_side(wasm_binary_target, dwarf_target)
 
   # replace placeholder strings with correct subresource locations
   if shared.Settings.SINGLE_FILE:

site/source/docs/tools_reference/emcc.rst

@@ -114,10 +114,11 @@ Options that are modified or new in *emcc* are listed below:
   - When compiling to object files, this is the same as in *Clang* and *gcc*, it adds debug information to the object files.
   - When linking, this is equivalent to :ref:`-g3 <emcc-g3>`.
 
-``-gseparate-dwarf``
+``-gseparate-dwarf[=FILENAME]``
   Preserve debug information, but in a separate file on the side. This is the
-  same as ``-g``, but the main file will contain no debug info, while a file
-  with suffix ``.debug.wasm`` will contain the debug info.
+  same as ``-g``, but the main file will contain no debug info, while debug
+  info will be present in a file on the side (``FILENAME`` if provided,
+  otherwise the same as the wasm file but with suffix ``.debug.wasm``).
 
 .. _emcc-gN:
 

tests/test_other.py

@@ -9147,6 +9147,16 @@ def test_separate_dwarf(self):
       self.assertIn(b'external_debug_info', wasm)
       self.assertIn(b'a.out.wasm.debug.wasm', wasm)
 
+  @no_fastcomp('dwarf')
+  def test_separate_dwarf_with_filename(self):
+    run_process([PYTHON, EMCC, path_from_root('tests', 'hello_world.c'), '-gseparate-dwarf=with_dwarf.wasm'])
+    self.assertNotExists('a.out.wasm.debug.wasm')
+    self.assertExists('with_dwarf.wasm')
+    # the correct notation is to have exactly one '=' and in the right place
+    for invalid in ('-gseparate-dwarf=x=', '-gseparate-dwarfy=', '-gseparate-dwarf-hmm'):
+      stderr = self.expect_fail([PYTHON, EMCC, path_from_root('tests', 'hello_world.c'), invalid])
+      self.assertContained('invalid -gseparate-dwarf=FILENAME notation', stderr)
+
   def test_wasm_producers_section(self):
     # no producers section by default
     run_process([PYTHON, EMCC, path_from_root('tests', 'hello_world.c')])

tools/shared.py

@@ -2704,12 +2704,11 @@ def wasm2js(js_file, wasm_file, opt_level, minify_whitespace, use_closure_compil
     return js_file
 
   @staticmethod
-  def emit_debug_on_side(wasm_file):
+  def emit_debug_on_side(wasm_file, wasm_file_with_dwarf):
     # extract the DWARF info from the main file, and leave the wasm with
     # debug into as a file on the side
     # TODO: emit only debug sections in the side file, and not the entire
     #       wasm as well
-    wasm_file_with_dwarf = wasm_file + '.debug.wasm'
     shutil.move(wasm_file, wasm_file_with_dwarf)
     run_process([LLVM_OBJCOPY, '--remove-section=.debug*', wasm_file_with_dwarf, wasm_file])