[gcc r11-9979] libstdc++: Don't use std::tolower in <charconv> [PR103911]

[gcc r11-9979] libstdc++: Don't use std::tolower in <charconv> [PR103911]

[Patrick Palka]

https://gcc.gnu.org/g:39099827b0f731b5f2da696f6f580156c8a7819c

commit r11-9979-g39099827b0f731b5f2da696f6f580156c8a7819c
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon May 2 07:01:33 2022 -0400

    libstdc++: Don't use std::tolower in <charconv> [PR103911]
    
    As with std::isdigit in r12-6281-gc83ecfbe74a5cf, we shouldn't be using
    std::tolower in <charconv> either.
    
            PR libstdc++/103911
    
    libstdc++-v3/ChangeLog:
    
            * src/c++17/floating_from_chars.cc (find_end_of_float): Accept
            two delimeters for the exponent part in the form of a possibly
            NULL string of length two.  Don't use std::tolower.
            (pattern): Adjust calls to find_end_of_float accordingly.
    
    (cherry picked from commit 86d821ddf5615e693ead667b2580898f46de8eb9)

Diff:
---
 libstdc++-v3/src/c++17/floating_from_chars.cc | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/libstdc++-v3/src/c++17/floating_from_chars.cc b/libstdc++-v3/src/c++17/floating_from_chars.cc
index f815e4981dd..ca1ad84e2ca 100644
--- a/libstdc++-v3/src/c++17/floating_from_chars.cc
+++ b/libstdc++-v3/src/c++17/floating_from_chars.cc
@@ -37,7 +37,6 @@
 #include <cmath>
 #include <cstdlib>
 #include <cstring>
-#include <cctype>
 #include <locale.h>
 #include <bits/functexcept.h>
 #if _GLIBCXX_HAVE_XLOCALE_H
@@ -115,10 +114,10 @@ namespace
 
   // Find initial portion of [first, last) containing a floating-point number.
   // The string `digits` is either `dec_digits` or `hex_digits`
-  // and `exp` is 'e' or 'p' or '\0'.
+  // and `exp` is "eE", "pP" or NULL.
   const char*
   find_end_of_float(const char* first, const char* last, const char* digits,
-		    char exp)
+		    const char *exp)
   {
     while (first < last && strchr(digits, *first) != nullptr)
       ++first;
@@ -128,7 +127,7 @@ namespace
 	while (first < last && strchr(digits, *first))
 	  ++first;
       }
-    if (first < last && exp != 0 && std::tolower((unsigned char)*first) == exp)
+    if (first < last && exp != nullptr && (*first == exp[0] || *first == exp[1]))
       {
 	++first;
 	if (first < last && (*first == '-' || *first == '+'))
@@ -210,7 +209,7 @@ namespace
 
 	if ((last - first + 2) > buffer_resource::guaranteed_capacity())
 	  {
-	    last = find_end_of_float(first + neg, last, digits, 'p');
+	    last = find_end_of_float(first + neg, last, digits, "pP");
 #ifndef __cpp_exceptions
 	    if ((last - first + 2) > buffer_resource::guaranteed_capacity())
 	      {
@@ -234,7 +233,7 @@ namespace
 	if ((last - first) > buffer_resource::guaranteed_capacity())
 	  {
 	    last = find_end_of_float(first + neg, last, digits,
-				     "e"[fmt == chars_format::fixed]);
+				     fmt == chars_format::fixed ? nullptr : "eE");
 #ifndef __cpp_exceptions
 	    if ((last - first) > buffer_resource::guaranteed_capacity())
 	      {