[libc-commits] [PATCH] D106901: [libc] add strncmp to strings

[Michael Jones via Phabricator via libc-commits]

michaelrj added inline comments.


================
Comment at: libc/src/string/strncmp.cpp:24
+    ;
+  return *reinterpret_cast<const unsigned char *>(left) -
+         *reinterpret_cast<const unsigned char *>(right);
----------------
sivachandra wrote:
> Just pointing out as I am not sure what is right here: casting to `unsigned char` can remove the potential sign and lead to -1 > 0. Even `strcmp` is set up this way so may be clean up both of them in a follow up patch.
given that these are supposed to be strings, I would assume that `unsigned char` is correct. Testing with my system libc, it appears that this is what it does as well. I ran strncmp on the following char array: `[-1, 'a', '\0']` compared to `"abc"` with length 3 and got the value 158, which is 255 - 97 (`'a'` = 97).


Repository:
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  https://reviews.llvm.org/D106901/new/

https://reviews.llvm.org/D106901