[sanitizer] Fix crash on empty strings.

[vchigrin]

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_libcdep.cpp

360

After changes in https://reviews.llvm.org/D27574 AddressInfo::file field may be NULL here.

[eugenis]

LGTM, thank you

[vchigrin]

@eugenis - seems I don't have commit permission to llvm project. Could you commit this patch for me? I will be very grateful.
Thank you in advance!

[MaskRay]

In D95431#2524043, @vchigrin wrote:

@eugenis - seems I don't have commit permission to llvm project. Could you commit this patch for me? I will be very grateful.
Thank you in advance!

Now that we use Git, the new practice is to use git commit --amend --author= :) https://llvm.org/docs/DeveloperPolicy.html#commit-messages

[eugenis]

Done. Too bad phab/arc does not do it automatically, and the email does not show up anywhere in the UI, too. It's such a bother to extract it from the mail headers.

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_libcdep.cpp

while (true) {
     str = ParseFileLineInfo(info, str);
 
     // Functions and filenames can be "??", in which case we write 0
     // to address info to mark that names are unknown.
     if (0 == internal_strcmp(info->function, "??")) {
       InternalFree(info->function);
       info->function = 0;
     }
-    if (0 == internal_strcmp(info->file, "??")) {
+    if (info->file && 0 == internal_strcmp(info->file, "??")) {
       InternalFree(info->file);
       info->file = 0;
     }
   }
 }
 
 // Parses a two-line string in the following format:
 //   <symbol_name>
 //   <start_address> <size>