diff --git a/libc/src/string/memchr.cpp b/libc/src/string/memchr.cpp
--- a/libc/src/string/memchr.cpp
+++ b/libc/src/string/memchr.cpp
@@ -17,7 +17,8 @@
 // TODO: Look at performance benefits of comparing words.
 LLVM_LIBC_FUNCTION(void *, memchr, (const void *src, int c, size_t n)) {
   return internal::find_first_character(
-      reinterpret_cast<const unsigned char *>(src), c, n);
+      reinterpret_cast<const unsigned char *>(src),
+      static_cast<unsigned char>(c), n);
 }
 
 } // namespace __llvm_libc
diff --git a/libc/src/string/memrchr.cpp b/libc/src/string/memrchr.cpp
--- a/libc/src/string/memrchr.cpp
+++ b/libc/src/string/memrchr.cpp
@@ -14,11 +14,10 @@
 
 LLVM_LIBC_FUNCTION(void *, memrchr, (const void *src, int c, size_t n)) {
   const unsigned char *str = reinterpret_cast<const unsigned char *>(src);
-  const unsigned char ch = c;
+  const unsigned char ch = static_cast<unsigned char>(c);
   for (; n != 0; --n) {
-    const unsigned char *s = str + n - 1;
-    if (*s == ch)
-      return const_cast<unsigned char *>(s);
+    if (*(--str) == ch)
+      return const_cast<unsigned char *>(str);
   }
   return nullptr;
 }
diff --git a/libc/src/string/strchr.cpp b/libc/src/string/strchr.cpp
--- a/libc/src/string/strchr.cpp
+++ b/libc/src/string/strchr.cpp
@@ -14,12 +14,12 @@
 
 // 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)
-    ;
-  return *str == ch ? reinterpret_cast<char *>(str) : nullptr;
+  const char ch = static_cast<char>(c);
+  for (; *src != ch; ++src)
+    if (*src == '\0')
+      return nullptr;
+
+  return const_cast<char *>(src);
 }
 
 } // namespace __llvm_libc
diff --git a/libc/src/string/string_utils.h b/libc/src/string/string_utils.h
--- a/libc/src/string/string_utils.h
+++ b/libc/src/string/string_utils.h
@@ -18,25 +18,26 @@
 // Returns the length of a string, denoted by the first occurrence
 // of a null terminator.
 static inline size_t string_length(const char *src) {
-  size_t length;
-  for (length = 0; *src; ++src, ++length)
+  const char *const initial = src;
+  for (; *src; ++src)
     ;
-  return length;
+  return src - initial;
 }
 
 // Returns the first occurrence of 'ch' within the first 'n' characters of
 // 'src'. If 'ch' is not found, returns nullptr.
 static inline void *find_first_character(const unsigned char *src,
                                          unsigned char ch, size_t n) {
-  for (; n && *src != ch; --n, ++src)
-    ;
-  return n ? const_cast<unsigned char *>(src) : nullptr;
+  for (; n != 0; --n, ++src)
+    if (*src == ch)
+      return const_cast<unsigned char *>(src);
+  return nullptr;
 }
 
 // Returns the maximum length span that contains only characters not found in
 // 'segment'. If no characters are found, returns the length of 'src'.
 static inline size_t complementary_span(const char *src, const char *segment) {
-  const char *initial = src;
+  const char *const initial = src;
   cpp::Bitset<256> bitset;
 
   for (; *segment; ++segment)
@@ -73,8 +74,7 @@
   for (; *src && !delimiter_set.test(*src); ++src)
     ;
   if (*src) {
-    *src = '\0';
-    ++src;
+    *src++ = '\0';
   }
   *saveptr = src;
   return token;
diff --git a/libc/src/string/strrchr.cpp b/libc/src/string/strrchr.cpp
--- a/libc/src/string/strrchr.cpp
+++ b/libc/src/string/strrchr.cpp
@@ -13,12 +13,12 @@
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(char *, strrchr, (const char *src, int c)) {
-  const char ch = c;
+  const char ch = static_cast<char>(c);
   char *last_occurrence = nullptr;
   do {
     if (*src == ch)
       last_occurrence = const_cast<char *>(src);
-  } while (*src++);
+  } while (*src++ != '\0');
   return last_occurrence;
 }