configuration: Constify more pointers

This continues the patch series constifying various pointers in the
configuration sub-system.

This is done as a separate commit as it involved a _slightly_ more
invasive change in nxt_conf_get_string().

While it takes a value parameter that is never modified, simply making
it const results in

  CC     build/src/nxt_conf.o
src/nxt_conf.c: In function ‘nxt_conf_get_string’:
src/nxt_conf.c:170:20: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  170 |         str->start = value->u.str.start;
      |                    ^

due to the assignment operator. Making value const will allow for
numerous other constification and seeing as we are not modifying it,
seems worthwhile.

We can get around the warning by casting ->u.{str,string}.start

Reviewed-by: Zhidao HONG <z.hong@f5.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

1 files changed, 23 insertions, 20 deletions

diff --git a/src/nxt_conf.c b/src/nxt_conf.c
index 3e9f9f4a..bb229c33 100644
--- a/src/nxt_conf.c
+++ b/src/nxt_conf.c
@@ -130,16 +130,17 @@ static nxt_int_t nxt_conf_copy_array(nxt_mp_t *mp, const nxt_conf_op_t *op,
 static nxt_int_t nxt_conf_copy_object(nxt_mp_t *mp, const nxt_conf_op_t *op,
     nxt_conf_value_t *dst, const nxt_conf_value_t *src);
 
-static size_t nxt_conf_json_string_length(nxt_conf_value_t *value);
-static u_char *nxt_conf_json_print_string(u_char *p, nxt_conf_value_t *value);
-static size_t nxt_conf_json_array_length(nxt_conf_value_t *value,
+static size_t nxt_conf_json_string_length(const nxt_conf_value_t *value);
+static u_char *nxt_conf_json_print_string(u_char *p,
+    const nxt_conf_value_t *value);
+static size_t nxt_conf_json_array_length(const nxt_conf_value_t *value,
     nxt_conf_json_pretty_t *pretty);
-static u_char *nxt_conf_json_print_array(u_char *p, nxt_conf_value_t *value,
-    nxt_conf_json_pretty_t *pretty);
-static size_t nxt_conf_json_object_length(nxt_conf_value_t *value,
-    nxt_conf_json_pretty_t *pretty);
-static u_char *nxt_conf_json_print_object(u_char *p, nxt_conf_value_t *value,
+static u_char *nxt_conf_json_print_array(u_char *p,
+    const nxt_conf_value_t *value, nxt_conf_json_pretty_t *pretty);
+static size_t nxt_conf_json_object_length(const nxt_conf_value_t *value,
     nxt_conf_json_pretty_t *pretty);
+static u_char *nxt_conf_json_print_object(u_char *p,
+    const nxt_conf_value_t *value, nxt_conf_json_pretty_t *pretty);
 
 static size_t nxt_conf_json_escape_length(u_char *p, size_t size);
 static u_char *nxt_conf_json_escape(u_char *dst, u_char *src, size_t size);
@@ -162,21 +163,22 @@ nxt_conf_json_indentation(u_char *p, uint32_t level)
 
 
 void
-nxt_conf_get_string(nxt_conf_value_t *value, nxt_str_t *str)
+nxt_conf_get_string(const nxt_conf_value_t *value, nxt_str_t *str)
 {
     if (value->type == NXT_CONF_VALUE_SHORT_STRING) {
         str->length = value->u.str.length;
-        str->start = value->u.str.start;
+        str->start = (u_char *) value->u.str.start;
 
     } else {
         str->length = value->u.string.length;
-        str->start = value->u.string.start;
+        str->start = (u_char *) value->u.string.start;
     }
 }
 
 
 nxt_str_t *
-nxt_conf_get_string_dup(nxt_conf_value_t *value, nxt_mp_t *mp, nxt_str_t *str)
+nxt_conf_get_string_dup(const nxt_conf_value_t *value, nxt_mp_t *mp,
+    nxt_str_t *str)
 {
     nxt_str_t  s;
 
@@ -2233,7 +2235,8 @@ nxt_conf_json_parse_error(nxt_conf_json_error_t *error, u_char *pos,
 
 
 size_t
-nxt_conf_json_length(nxt_conf_value_t *value, nxt_conf_json_pretty_t *pretty)
+nxt_conf_json_length(const nxt_conf_value_t *value,
+    nxt_conf_json_pretty_t *pretty)
 {
     switch (value->type) {
 
@@ -2265,7 +2268,7 @@ nxt_conf_json_length(nxt_conf_value_t *value, nxt_conf_json_pretty_t *pretty)
 
 
 u_char *
-nxt_conf_json_print(u_char *p, nxt_conf_value_t *value,
+nxt_conf_json_print(u_char *p, const nxt_conf_value_t *value,
     nxt_conf_json_pretty_t *pretty)
 {
     switch (value->type) {
@@ -2299,7 +2302,7 @@ nxt_conf_json_print(u_char *p, nxt_conf_value_t *value,
 
 
 static size_t
-nxt_conf_json_string_length(nxt_conf_value_t *value)
+nxt_conf_json_string_length(const nxt_conf_value_t *value)
 {
     nxt_str_t  str;
 
@@ -2310,7 +2313,7 @@ nxt_conf_json_string_length(nxt_conf_value_t *value)
 
 
 static u_char *
-nxt_conf_json_print_string(u_char *p, nxt_conf_value_t *value)
+nxt_conf_json_print_string(u_char *p, const nxt_conf_value_t *value)
 {
     nxt_str_t  str;
 
@@ -2327,7 +2330,7 @@ nxt_conf_json_print_string(u_char *p, nxt_conf_value_t *value)
 
 
 static size_t
-nxt_conf_json_array_length(nxt_conf_value_t *value,
+nxt_conf_json_array_length(const nxt_conf_value_t *value,
     nxt_conf_json_pretty_t *pretty)
 {
     size_t            len;
@@ -2369,7 +2372,7 @@ nxt_conf_json_array_length(nxt_conf_value_t *value,
 
 
 static u_char *
-nxt_conf_json_print_array(u_char *p, nxt_conf_value_t *value,
+nxt_conf_json_print_array(u_char *p, const nxt_conf_value_t *value,
     nxt_conf_json_pretty_t *pretty)
 {
     nxt_uint_t        n;
@@ -2421,7 +2424,7 @@ nxt_conf_json_print_array(u_char *p, nxt_conf_value_t *value,
 
 
 static size_t
-nxt_conf_json_object_length(nxt_conf_value_t *value,
+nxt_conf_json_object_length(const nxt_conf_value_t *value,
     nxt_conf_json_pretty_t *pretty)
 {
     size_t                    len;
@@ -2465,7 +2468,7 @@ nxt_conf_json_object_length(nxt_conf_value_t *value,
 
 
 static u_char *
-nxt_conf_json_print_object(u_char *p, nxt_conf_value_t *value,
+nxt_conf_json_print_object(u_char *p, const nxt_conf_value_t *value,
     nxt_conf_json_pretty_t *pretty)
 {
     nxt_uint_t                n;