[Build] extract_unwind_tables.py: Remove temp file usage.

extract_unwind_tables.py calls dump_syms, and processes ~400 MB of
data from ~105 M lines. Previously these data were written to a temp
file, which is then opened and read line-by-line. This approach creates
churn, and is prone to out-of-disk-space problem.

This CL removes temp file usage by directly piping dump_syms output to
_ParseCfiData(), using subprocess.Popen(bufsize=-1)'s |stdout|. Run time
is unaffected.

Fixed: 1068862
Change-Id: Iaa0d433dcb91a8b15fff4dd6ce0a34fcba8d6376
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2141220
Commit-Queue: Samuel Huang <huangs@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757740}

build/android/gyp/extract_unwind_tables.py

@@ -254,10 +254,8 @@ def _WriteCfiData(cfi_data, out_file):
     _Write2Bytes(out_file, data)
 
 
-def _ParseCfiData(sym_file, output_path):
-  with open(sym_file, 'r') as f:
-    cfi_data =  _GetAllCfiRows(f)
-
+def _ParseCfiData(sym_stream, output_path):
+  cfi_data = _GetAllCfiRows(sym_stream)
   with open(output_path, 'wb') as out_file:
     _WriteCfiData(cfi_data, out_file)
 
@@ -275,13 +273,11 @@ def main():
       help='The path of the dump_syms binary')
 
   args = parser.parse_args()
+  cmd = ['./' + args.dump_syms_path, args.input_path]
+  proc = subprocess.Popen(cmd, bufsize=-1, stdout=subprocess.PIPE)
+  _ParseCfiData(proc.stdout, args.output_path)
+  assert proc.wait() == 0
 
-  with tempfile.NamedTemporaryFile() as sym_file:
-    out = subprocess.call(
-        ['./' +args.dump_syms_path, args.input_path], stdout=sym_file)
-    assert not out
-    sym_file.flush()
-    _ParseCfiData(sym_file.name, args.output_path)
   return 0
 
 if __name__ == '__main__':

build/android/gyp/extract_unwind_tables_tests.py

@@ -24,9 +24,8 @@ from util import build_utils
 
 class TestExtractUnwindTables(unittest.TestCase):
   def testExtractCfi(self):
-    with tempfile.NamedTemporaryFile() as input_file, \
-        tempfile.NamedTemporaryFile() as output_file:
-      input_file.write("""
+    with tempfile.NamedTemporaryFile() as output_file:
+      test_data_lines = """
 MODULE Linux arm CDE12FE1DF2B37A9C6560B4CBEE056420 lib_chrome.so
 INFO CODE_ID E12FE1CD2BDFA937C6560B4CBEE05642
 FILE 0 ../../base/allocator/allocator_check.cc
@@ -63,9 +62,8 @@ STACK CFI INIT 3b92114 6c .cfa: sp 0 + .ra: lr
 STACK CFI 3b92118 .cfa: r7 16 + .ra: .cfa -20 + ^
 STACK CFI INIT 3b93214 fffff .cfa: sp 0 + .ra: lr
 STACK CFI 3b93218 .cfa: r7 16 + .ra: .cfa -4 + ^
-""")
-      input_file.flush()
-      extract_unwind_tables._ParseCfiData(input_file.name, output_file.name)
+""".splitlines()
+      extract_unwind_tables._ParseCfiData(test_data_lines, output_file.name)
 
       expected_cfi_data = {
         0xe1a1e4 : [0x2, 0x11, 0x4, 0x50],