build: fix char signed vs unsigned warning (#23675)

char defaults to signed on most x86 platforms, but unsigned on arm64.
When targeting linux arm64 this produced a warning because character was
always >= 0. This change circumvents this warning without changing
behavior even though it seems pretty unreasonable to have a character
less than 0 in this use case. Theoretically we could disable a warning
flag instead but that differs between clang and gcc.

Fixes #23569

Signed-off-by: Keith Smiley <[email protected]>

Signed-off-by: Keith Smiley <[email protected]>

Author: keith

source/common/common/json_escape_string.h

@@ -64,7 +64,7 @@ class JsonEscaper {
         position += 2;
         break;
       default:
-        if (character >= 0x00 && character <= 0x1f) {
+        if (character == 0x00 || (character > 0x00 && character <= 0x1f)) {
           // Print character as unicode hex.
           sprintf(&result[position + 1], "u%04x", static_cast<int>(character));
           position += 6;
@@ -107,7 +107,7 @@ class JsonEscaper {
       }
 
       default: {
-        if (character >= 0x00 && character <= 0x1f) {
+        if (character == 0x00 || (character > 0x00 && character <= 0x1f)) {
           // From character (1 byte) to unicode hex (6 bytes).
           result += 5;
         }