Fix GCC 15 Wunterminated-string-initialization issues

When building with the upcoming GCC 15, we are hit by the new
Wunterminated-string-initialization compiler warning (however, due to
-Werror, this is a build failure). E.g.

  src/nxt_string.c: In function ‘nxt_encode_uri’:
  src/nxt_string.c:601:36: error: initializer-string for array of ‘unsigned char’ is too long [-Werror=unterminated-string-initialization]
    601 |     static const u_char  hex[16] = "0123456789ABCDEF";
        |                                    ^~~~~~~~~~~~~~~~~~

We have created a character array containing 16 elements, but is not NUL
terminated. While this type of (lookup/translation table) use case is
perfectly valid and we could simply disable the warning, it is probably
still a useful warning to have enabled.

There is a 'nonstring' attribute, but that doesn't influence this
warning.

Lets just do what nginx does and create them NUL terminated. Except in
src/nxt_http_parse.c where they *really* want to be non-NUL
terminated and we use *arrays* of chars.

Signed-off-by: Andrew Clayton <[email protected]>

src/nxt_http_parse.c

@@ -164,8 +164,10 @@ nxt_http_parse_request_line(nxt_http_request_parse_t *rp, u_char **pos,
     nxt_http_ver_t           ver;
     nxt_http_target_traps_e  trap;
 
-    static const nxt_http_ver_t  http11 = { "HTTP/1.1" };
-    static const nxt_http_ver_t  http10 = { "HTTP/1.0" };
+    static const nxt_http_ver_t  http11 =
+                            {{ 'H', 'T', 'T', 'P', '/', '1', '.', '1' }};
+    static const nxt_http_ver_t  http10 =
+                            {{ 'H', 'T', 'T', 'P', '/', '1', '.', '0' }};
 
     p = *pos;
 
@@ -516,7 +518,8 @@ nxt_http_parse_field_name(nxt_http_request_parse_t *rp, u_char **pos,
     size_t    len;
     uint32_t  hash;
 
-    static const u_char  normal[256]  nxt_aligned(64) =
+    /* The last '\0' is not needed because the string is NUL terminated */
+    static const u_char  normal[]  nxt_aligned(64) =
         "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
     /*   \s ! " # $ % & ' ( ) * + ,        . /                 : ; < = > ?   */
         "\0\1\0\1\1\1\1\1\0\0\1\1\0" "-" "\1\0" "0123456789" "\0\0\0\0\0\0"
@@ -529,7 +532,7 @@ nxt_http_parse_field_name(nxt_http_request_parse_t *rp, u_char **pos,
         "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
         "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
         "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
-        "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+        "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
 
     p = *pos + rp->field_name.length;
     hash = rp->field_hash;

src/nxt_sprintf.c

@@ -112,8 +112,8 @@ nxt_vsprintf(u_char *buf, u_char *end, const char *fmt, va_list args)
     nxt_sprintf_t        spf;
     nxt_file_name_t      *fn;
 
-    static const u_char  hexadecimal[16] = "0123456789abcdef";
-    static const u_char  HEXADECIMAL[16] = "0123456789ABCDEF";
+    static const u_char  hexadecimal[] = "0123456789abcdef";
+    static const u_char  HEXADECIMAL[] = "0123456789ABCDEF";
     static const u_char  nan[] = "[nan]";
     static const u_char  null[] = "[null]";
     static const u_char  infinity[] = "[infinity]";

src/nxt_string.c

@@ -592,14 +592,15 @@ nxt_decode_uri_plus(u_char *dst, u_char *src, size_t length)
 }
 
 
+static const u_char  nxt_hex[] = "0123456789ABCDEF";
+
+
 uintptr_t
 nxt_encode_uri(u_char *dst, u_char *src, size_t length)
 {
     u_char      *end;
     nxt_uint_t  n;
 
-    static const u_char  hex[16] = "0123456789ABCDEF";
-
     end = src + length;
 
     if (dst == NULL) {
@@ -624,8 +625,8 @@ nxt_encode_uri(u_char *dst, u_char *src, size_t length)
 
         if (nxt_uri_escape[*src >> 5] & (1U << (*src & 0x1f))) {
             *dst++ = '%';
-            *dst++ = hex[*src >> 4];
-            *dst++ = hex[*src & 0xf];
+            *dst++ = nxt_hex[*src >> 4];
+            *dst++ = nxt_hex[*src & 0xf];
 
         } else {
             *dst++ = *src;
@@ -644,8 +645,6 @@ nxt_encode_complex_uri(u_char *dst, u_char *src, size_t length)
     u_char      *reserved, *end, ch;
     nxt_uint_t  n;
 
-    static const u_char  hex[16] = "0123456789ABCDEF";
-
     reserved = (u_char *) "?#\0";
 
     end = src + length;
@@ -689,8 +688,8 @@ nxt_encode_complex_uri(u_char *dst, u_char *src, size_t length)
 
             } else {
                 *dst++ = '%';
-                *dst++ = hex[ch >> 4];
-                *dst++ = hex[ch & 0xf];
+                *dst++ = nxt_hex[ch >> 4];
+                *dst++ = nxt_hex[ch & 0xf];
                 continue;
             }
         }