Fix IOError exception being raised in `asan_symbolize.py`crash when

using `atos` symbolizer on Darwin when the binaries don't exist.

For now we just produce an unsymbolicated stackframe when the binary
doesn't exist.

llvm-svn: 348659

compiler-rt/lib/asan/scripts/asan_symbolize.py

@@ -231,6 +231,10 @@ class DarwinSymbolizer(Symbolizer):
     """Overrides Symbolizer.symbolize."""
     if self.binary != binary:
       return None
+    if not os.path.exists(binary):
+      # If the binary doesn't exist atos will exit which will lead to IOError
+      # exceptions being raised later on so just don't try to symbolize.
+      return ['{} ({}:{}+{})'.format(addr, binary, self.arch, offset)]
     atos_line = self.atos.convert('0x%x' % int(offset, 16))
     while "got symbolicator for" in atos_line:
       atos_line = self.atos.readline()