Declare non-local variables as const where possible

Having non-const variables of static lifetime or even global scope is
usually a bad idea. These variables are inherently constants, and this
should be enforced.

This required marking some functions as not modifying input parameters
and marking some pointers as pointers to const.

One advantage is that the compiler usually puts const static variables
in a read-only code segment, so they can't be modified physically.
This can be verified with `nm` (on POSIX systems).

To avoid changes to the public API, functions returning non-const
pointers to data tables were left intact, but the returned data may not
be modified. Internally we prefer using the proj_list_* functions over
the pj_get_*_ref functions, because the former return const pointers.

1 files changed, 1 insertions, 18 deletions

diff --git a/src/proj_4D_api.c b/src/proj_4D_api.c
index 0fba5097..a0550727 100644
--- a/src/proj_4D_api.c
+++ b/src/proj_4D_api.c
@@ -597,7 +597,7 @@ PJ_INFO proj_info(void) {
 
 ******************************************************************************/
     PJ_INFO info;
-    const char **paths;
+    const char * const *paths;
     char *tmpstr;
     int i, n;
     size_t len = 0;
@@ -847,20 +847,3 @@ PJ_FACTORS proj_factors(PJ *P, LP lp) {
     return factors;
 }
 
-
-const PJ_ELLPS *proj_list_ellps(void) {
-    return pj_get_ellps_ref();
-}
-
-const PJ_UNITS *proj_list_units(void) {
-    return pj_get_units_ref();
-}
-
-const PJ_OPERATIONS *proj_list_operations(void) {
-    return pj_get_list_ref();
-}
-
-const PJ_PRIME_MERIDIANS *proj_list_prime_meridians(void) {
-    return pj_get_prime_meridians_ref();
-}
-