[Lldb-commits] [PATCH] D30918: [debugserver] This is a small cleanup patch to AVX support detection

[Jason Molenda via Phabricator via lldb-commits]

jasonmolenda requested changes to this revision.
jasonmolenda added a comment.
This revision now requires changes to proceed.

Looks good, a few small suggestions from reading the code afresh.  I'm not sure how many open source contributors we may have running macOS 10.6 or earlier (or macOS 10.7.[1-3]) but keeping this code is probably still a good idea at this point.



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Comment at: tools/debugserver/source/MacOSX/x86_64/DNBArchImplX86_64.cpp:66
+  int error = ::sysctlbyname(feature, &answer, &answer_size, NULL, 0);
+  return !error & answer;
+}
----------------
I see what you're doing -- this can either return "false, meaning the sysctlbyname failed or I got a zero value, or true meaning it succeeded and I got a nonzero value" but the use of a bitwise AND is going to look like a bug to any casual reader and make them re-read the code a few times before they've realized it is intended (at least it did me).  It might be easier for future maintainers if it's written more like like

if (error != 0 && answer != 0)
  return true;
else
  return false;

and let the compiler come up with the shorter form when generating the instructions.


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Comment at: tools/debugserver/source/MacOSX/x86_64/DNBArchImplX86_64.cpp:99
+  for (; first_letter < length; ++first_letter) {
+    if (buffer[first_letter] & 0x40)
+      break;
----------------
Would '@' be clearer here than 0x40?  I had to run man ascii to figure out what this was.  Maybe a comment saying that we expect the string from KERN_OSVERSION to be something like '11B156' & we're interested in the '11' bit would make it a little easier to read. (I had to run sysctl to look at the string you're parsing to follow along with the logic)


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Comment at: tools/debugserver/source/MacOSX/x86_64/DNBArchImplX86_64.cpp:103
+  char letter = buffer[first_letter];
+  buffer[first_letter] = 0;
+  auto major_ver = strtoull(buffer, NULL, 0);
----------------
Not a big deal but '\0'.


https://reviews.llvm.org/D30918