SDL: dynapi: Abstract out the environment variable name.

From 69f0223474374c174d788395b43022e8b7c78954 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 29 Nov 2022 14:13:02 -0500
Subject: [PATCH] dynapi: Abstract out the environment variable name.

(cherry picked from commit cc487ffb801f862aec7e2b415e74c563c4d528d5)
---
 src/dynapi/SDL_dynapi.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/dynapi/SDL_dynapi.c b/src/dynapi/SDL_dynapi.c
index 9a7e4c994329..936c1a0f82f2 100644
--- a/src/dynapi/SDL_dynapi.c
+++ b/src/dynapi/SDL_dynapi.c
@@ -24,6 +24,8 @@
 
 #if SDL_DYNAMIC_API
 
+#define SDL_DYNAMIC_API_ENVVAR "SDL_DYNAMIC_API"
+
 #if defined(__OS2__)
 #define INCL_DOS
 #define INCL_DOSERRORS
@@ -400,21 +402,21 @@ SDL_NORETURN void SDL_ExitProcess(int exitcode);
 static void
 SDL_InitDynamicAPILocked(void)
 {
-    const char *libname = SDL_getenv_REAL("SDL_DYNAMIC_API");
+    const char *libname = SDL_getenv_REAL(SDL_DYNAMIC_API_ENVVAR);
     SDL_DYNAPI_ENTRYFN entry = NULL;  /* funcs from here by default. */
     SDL_bool use_internal = SDL_TRUE;
 
     if (libname) {
         entry = (SDL_DYNAPI_ENTRYFN) get_sdlapi_entry(libname, "SDL_DYNAPI_entry");
         if (!entry) {
-            dynapi_warn("Couldn't load overriding SDL library. Please fix or remove the SDL_DYNAMIC_API environment variable. Using the default SDL.");
+            dynapi_warn("Couldn't load overriding SDL library. Please fix or remove the " SDL_DYNAMIC_API_ENVVAR " environment variable. Using the default SDL.");
             /* Just fill in the function pointers from this library, later. */
         }
     }
 
     if (entry) {
         if (entry(SDL_DYNAPI_VERSION, &jump_table, sizeof (jump_table)) < 0) {
-            dynapi_warn("Couldn't override SDL library. Using a newer SDL build might help. Please fix or remove the SDL_DYNAMIC_API environment variable. Using the default SDL.");
+            dynapi_warn("Couldn't override SDL library. Using a newer SDL build might help. Please fix or remove the " SDL_DYNAMIC_API_ENVVAR " environment variable. Using the default SDL.");
             /* Just fill in the function pointers from this library, later. */
         } else {
             use_internal = SDL_FALSE;   /* We overrode SDL! Don't use the internal version! */