[libc] s/NULL/nullptr (#86867)

Otherwise we need to pull in stddef.h for the declaration of NULL.

Author: nickdesaulniers

libc/src/__support/char_vector.h

@@ -11,8 +11,8 @@
 
 #include "src/__support/common.h" // LIBC_INLINE
 
-#include <stddef.h>
-#include <stdlib.h> // For allocation.
+#include <stddef.h> // size_t
+#include <stdlib.h> // malloc, realloc, free
 
 namespace LIBC_NAMESPACE {
 
@@ -46,7 +46,7 @@ class CharVector {
       if (cur_str == local_buffer) {
         char *new_str;
         new_str = reinterpret_cast<char *>(malloc(cur_buff_size));
-        if (new_str == NULL) {
+        if (new_str == nullptr) {
           return false;
         }
         // TODO: replace with inline memcpy
@@ -55,7 +55,7 @@ class CharVector {
         cur_str = new_str;
       } else {
         cur_str = reinterpret_cast<char *>(realloc(cur_str, cur_buff_size));
-        if (cur_str == NULL) {
+        if (cur_str == nullptr) {
           return false;
         }
       }

libc/src/stdlib/str_from_util.h

@@ -11,7 +11,7 @@
 // %{a,A,e,E,f,F,g,G}, are not allowed and any code that does otherwise results
 // in undefined behaviour(including use of a '%%' conversion specifier); which
 // in this case is that the buffer string is simply populated with the format
-// string. The case of the input being NULL should be handled in the calling
+// string. The case of the input being nullptr should be handled in the calling
 // function (strfromf, strfromd, strfroml) itself.
 
 #ifndef LLVM_LIBC_SRC_STDLIB_STRFROM_UTIL_H

libc/src/stdlib/strtod.cpp

@@ -19,7 +19,7 @@ LLVM_LIBC_FUNCTION(double, strtod,
   if (result.has_error())
     libc_errno = result.error;
 
-  if (str_end != NULL)
+  if (str_end != nullptr)
     *str_end = const_cast<char *>(str + result.parsed_len);
 
   return result.value;

libc/src/stdlib/strtof.cpp

@@ -19,7 +19,7 @@ LLVM_LIBC_FUNCTION(float, strtof,
   if (result.has_error())
     libc_errno = result.error;
 
-  if (str_end != NULL)
+  if (str_end != nullptr)
     *str_end = const_cast<char *>(str + result.parsed_len);
 
   return result.value;

libc/src/stdlib/strtold.cpp

@@ -19,7 +19,7 @@ LLVM_LIBC_FUNCTION(long double, strtold,
   if (result.has_error())
     libc_errno = result.error;
 
-  if (str_end != NULL)
+  if (str_end != nullptr)
     *str_end = const_cast<char *>(str + result.parsed_len);
 
   return result.value;