[libc][NFC] Make strchr and strrchr more consistent

[sivachandra]

libc/src/string/strrchr.cpp

16

Same here - keep this char instead of unsigned char. If it is unsigned char, then you end up comparing singed and unsigned values on line 19.

[sivachandra]

libc/src/string/strchr.cpp

16–17

I had added a comment here but Phabricator ignored it for some reason.

I had pointed out that the standard actually says we should compare with characters in src after converting c to char. So, make this char instead of unsigned char. You will not need a cast on line 18.

[michaelrj]

change to comparing signed chars

libc/src/string/strchr.cpp

 //===-- Implementation of strchr ------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/strchr.h"
 
 #include "src/__support/common.h"
 
 namespace __llvm_libc {
 
 // TODO: Look at performance benefits of comparing words.
 LLVM_LIBC_FUNCTION(char *, strchr, (const char *src, int c)) {
-  unsigned char *str =
-      const_cast<unsigned char *>(reinterpret_cast<const unsigned char *>(src));
-  const unsigned char ch = c;
-  for (; *str && *str != ch; ++str)
+  const char ch = c;
+  for (; *src && *src != ch; ++src)
     ;
-  return *str == ch ? reinterpret_cast<char *>(str) : nullptr;
+  return *src == ch ? const_cast<char *>(src) : nullptr;
 }
 
 } // namespace __llvm_libc

libc/src/string/strrchr.cpp

 //===-- Implementation of strrchr------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/strrchr.h"
 
 #include "src/__support/common.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(char *, strrchr, (const char *src, int c)) {
   const char ch = c;
   char *last_occurrence = nullptr;
-  do {
+  for (; *src; ++src) {
     if (*src == ch)
       last_occurrence = const_cast<char *>(src);
-  } while (*src++);
+  }
   return last_occurrence;
 }
 
 } // namespace __llvm_libc