147 lines
4.9 KiB
Python
147 lines
4.9 KiB
Python
#!/usr/bin/env python
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"""wrapper around emcc link step.
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This wrapper currently serves the following purposes.
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1. Ensures we always link to file with .js extension. The upstream default
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it to link to an llvm bitcode file which is never (AFAICT) want to do that.
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2. When building with --config=wasm the final output is multiple files, usually
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at least one .js and one .wasm file. Since the cc_binary link step only
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allows a single output, we must tar up the outputs into a single file.
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3. Add quotes around arguments that need them in the response file to work
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around a bazel quirk.
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"""
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from __future__ import print_function
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import os
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import subprocess
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import sys
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# Only argument should be @path/to/parameter/file
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assert sys.argv[1][0] == '@'
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param_filename = sys.argv[1][1:]
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param_file_args = [l.strip() for l in open(param_filename, 'r').readlines()]
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output_index = param_file_args.index('-o') + 1
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orig_output = js_output = param_file_args[output_index]
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outdir = os.path.dirname(orig_output)
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# google3-only(TODO(b/139440956): Default to False once the bug is fixed)
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replace_response_file = any(' ' in a for a in param_file_args)
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if not os.path.splitext(orig_output)[1]:
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js_output = orig_output + '.js'
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param_file_args[output_index] = js_output
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replace_response_file = True
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# Re-write response file if needed.
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if replace_response_file:
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new_param_filename = param_filename + '.modified'
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with open(new_param_filename, 'w') as f:
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for param in param_file_args:
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if ' ' in param:
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f.write('"%s"' % param)
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else:
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f.write(param)
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f.write('\n')
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sys.argv[1] = '@' + new_param_filename
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emcc_py = os.path.join(os.environ['EMSCRIPTEN'], 'emcc.py')
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rtn = subprocess.call(['python3', emcc_py] + sys.argv[1:])
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if rtn != 0:
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sys.exit(1)
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js_name = os.path.basename(js_output)
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base_name = os.path.splitext(js_name)[0]
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files = []
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extensions = [
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'.js',
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'.wasm',
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'.wasm.map',
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'.js.mem',
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'.fetch.js',
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'.worker.js',
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'.data',
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'.js.symbols',
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'.wasm.debug.wasm'
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]
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for ext in extensions:
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filename = base_name + ext
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if os.path.exists(os.path.join(outdir, filename)):
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files.append(filename)
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wasm_base = os.path.join(outdir, base_name + '.wasm')
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if os.path.exists(wasm_base + '.debug.wasm') and os.path.exists(wasm_base):
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# If we have a .wasm.debug.wasm file and a .wasm file, we need to rewrite the
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# section in the .wasm file that refers to it. The path that's in there
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# is the blaze output path; we want it to be just the filename.
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llvm_objcopy = os.path.join(
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os.environ['EMSCRIPTEN'], 'llvm-bin/llvm-objcopy')
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# First, check to make sure the .wasm file has the header that needs to be
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# rewritten.
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rtn = subprocess.call([
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llvm_objcopy,
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'--dump-section=external_debug_info=/dev/null',
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wasm_base], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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if rtn == 0:
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# If llvm-objcopy did not return an error, the external_debug_info section
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# must exist, so we're good to continue.
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# Next we need to convert length of the filename to LEB128.
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# Start by converting the length of the filename to a bit string.
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bit_string = '{0:b}'.format(len(base_name + '.wasm.debug.wasm'))
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# Pad the bit string with 0s so that its length is a multiple of 7.
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while len(bit_string) % 7 != 0:
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bit_string = '0' + bit_string
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# Break up our bit string into chunks of 7.
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# We do this backwards because the final format is little-endian.
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final_bytes = bytearray()
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for i in reversed(range(0, len(bit_string), 7)):
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binary_part = bit_string[i:i + 7]
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if i != 0:
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# Every chunk except the last one needs to be prepended with '1'.
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# The length of each chunk is 7, so that one has an implicit '0'.
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binary_part = '1' + binary_part
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final_bytes.append(int(binary_part, 2))
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# Finally, add the actual filename.
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final_bytes.extend(base_name + '.wasm.debug.wasm')
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# Write our length + filename bytes to a temp file.
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with open('debugsection.tmp', 'wb+') as f:
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f.write(final_bytes)
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f.close()
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# First delete the old section.
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subprocess.check_call([
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llvm_objcopy,
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wasm_base,
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'--remove-section=external_debug_info'])
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# Rewrite section with the new size and filename from the temp file.
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subprocess.check_call([
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llvm_objcopy,
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wasm_base,
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'--add-section=external_debug_info=debugsection.tmp'])
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# If we have more than one output file then create tarball
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if len(files) > 1:
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cmd = ['tar', 'cf', 'tmp.tar'] + files
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subprocess.check_call(cmd, cwd=outdir)
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os.rename(os.path.join(outdir, 'tmp.tar'), orig_output)
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elif len(files) == 1:
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# Otherwise, if only have a single output than move it to the expected name
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if files[0] != os.path.basename(orig_output):
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os.rename(os.path.join(outdir, files[0]), orig_output)
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else:
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print('emcc.py did not appear to output any known files!')
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sys.exit(1)
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sys.exit(0)
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