diff --git a/include/SDL3/SDL_stdinc.h b/include/SDL3/SDL_stdinc.h
index 63c8d2aea9..6f9a3ed8e9 100644
--- a/include/SDL3/SDL_stdinc.h
+++ b/include/SDL3/SDL_stdinc.h
@@ -590,11 +590,13 @@ extern SDL_DECLSPEC int SDLCALL SDL_GetNumAllocations(void);
 extern SDL_DECLSPEC char *SDLCALL SDL_getenv(const char *name);
 extern SDL_DECLSPEC int SDLCALL SDL_setenv(const char *name, const char *value, int overwrite);
 
-extern SDL_DECLSPEC void SDLCALL SDL_qsort(void *base, size_t nmemb, size_t size, int (SDLCALL *compare) (const void *, const void *));
-extern SDL_DECLSPEC void * SDLCALL SDL_bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (SDLCALL *compare) (const void *, const void *));
+typedef int (SDLCALL *SDL_CompareCallback)(const void *a, const void *b);
+extern SDL_DECLSPEC void SDLCALL SDL_qsort(void *base, size_t nmemb, size_t size, SDL_CompareCallback compare);
+extern SDL_DECLSPEC void * SDLCALL SDL_bsearch(const void *key, const void *base, size_t nmemb, size_t size, SDL_CompareCallback compare);
 
-extern SDL_DECLSPEC void SDLCALL SDL_qsort_r(void *base, size_t nmemb, size_t size, int (SDLCALL *compare) (void *, const void *, const void *), void *userdata);
-extern SDL_DECLSPEC void * SDLCALL SDL_bsearch_r(const void *key, const void *base, size_t nmemb, size_t size, int (SDLCALL *compare) (void *, const void *, const void *), void *userdata);
+typedef int (SDLCALL *SDL_CompareCallback_r)(void *userdata, const void *a, const void *b);
+extern SDL_DECLSPEC void SDLCALL SDL_qsort_r(void *base, size_t nmemb, size_t size, SDL_CompareCallback_r compare, void *userdata);
+extern SDL_DECLSPEC void * SDLCALL SDL_bsearch_r(const void *key, const void *base, size_t nmemb, size_t size, SDL_CompareCallback_r compare, void *userdata);
 
 extern SDL_DECLSPEC int SDLCALL SDL_abs(int x);
 
diff --git a/include/SDL3/SDL_thread.h b/include/SDL3/SDL_thread.h
index 3502b8c154..aed8715df6 100644
--- a/include/SDL3/SDL_thread.h
+++ b/include/SDL3/SDL_thread.h
@@ -490,21 +490,34 @@ extern SDL_DECLSPEC SDL_TLSID SDLCALL SDL_CreateTLS(void);
  */
 extern SDL_DECLSPEC void * SDLCALL SDL_GetTLS(SDL_TLSID id);
 
+
+/**
+ * The callback used to cleanup data passed to SDL_SetTLS.
+ *
+ * This is called when a thread exits, to allow an app to
+ * free any resources.
+ *
+ * \param value a pointer previously handed to SDL_SetTLS.
+ *
+ * \since This datatype is available since SDL 3.0.0.
+ *
+ * \sa SDL_SetTLS
+ */
+typedef void (SDLCALL *SDL_TLSDestructorCallback)(void *value);
+
 /**
  * Set the current thread's value associated with a thread local storage ID.
  *
- * The function prototype for `destructor` is:
+ * Note that replacing a value from a previous call to this function on the
+ * same thread does _not_ call the previous value's destructor!
  *
- * ```c
- * void destructor(void *value)
- * ```
- *
- * where its parameter `value` is what was passed as `value` to SDL_SetTLS().
+ * `destructor` can be NULL; it is assumed that `value` does not need
+ * to be cleaned up if so.
  *
  * \param id the thread local storage ID
  * \param value the value to associate with the ID for the current thread
  * \param destructor a function called when the thread exits, to free the
- *                   value
+ *                   value. Can be NULL.
  * \returns 0 on success or a negative error code on failure; call
  *          SDL_GetError() for more information.
  *
@@ -512,7 +525,7 @@ extern SDL_DECLSPEC void * SDLCALL SDL_GetTLS(SDL_TLSID id);
  *
  * \sa SDL_GetTLS
  */
-extern SDL_DECLSPEC int SDLCALL SDL_SetTLS(SDL_TLSID id, const void *value, void (SDLCALL *destructor)(void*));
+extern SDL_DECLSPEC int SDLCALL SDL_SetTLS(SDL_TLSID id, const void *value, SDL_TLSDestructorCallback destructor);
 
 /**
  * Cleanup all TLS data for this thread.
diff --git a/src/dynapi/SDL_dynapi_procs.h b/src/dynapi/SDL_dynapi_procs.h
index df4f691cc7..5c32967050 100644
--- a/src/dynapi/SDL_dynapi_procs.h
+++ b/src/dynapi/SDL_dynapi_procs.h
@@ -775,7 +775,7 @@ SDL_DYNAPI_PROC(int,SDL_SetSurfaceColorMod,(SDL_Surface *a, Uint8 b, Uint8 c, Ui
 SDL_DYNAPI_PROC(int,SDL_SetSurfaceColorspace,(SDL_Surface *a, SDL_Colorspace b),(a,b),return)
 SDL_DYNAPI_PROC(int,SDL_SetSurfacePalette,(SDL_Surface *a, SDL_Palette *b),(a,b),return)
 SDL_DYNAPI_PROC(int,SDL_SetSurfaceRLE,(SDL_Surface *a, int b),(a,b),return)
-SDL_DYNAPI_PROC(int,SDL_SetTLS,(SDL_TLSID a, const void *b, void (SDLCALL *c)(void*)),(a,b,c),return)
+SDL_DYNAPI_PROC(int,SDL_SetTLS,(SDL_TLSID a, const void *b, SDL_TLSDestructorCallback c),(a,b,c),return)
 SDL_DYNAPI_PROC(int,SDL_SetTextInputRect,(const SDL_Rect *a),(a),return)
 SDL_DYNAPI_PROC(int,SDL_SetTextureAlphaMod,(SDL_Texture *a, Uint8 b),(a,b),return)
 SDL_DYNAPI_PROC(int,SDL_SetTextureAlphaModFloat,(SDL_Texture *a, float b),(a,b),return)
@@ -905,8 +905,8 @@ SDL_DYNAPI_PROC(float,SDL_atan2f,(float a, float b),(a,b),return)
 SDL_DYNAPI_PROC(float,SDL_atanf,(float a),(a),return)
 SDL_DYNAPI_PROC(double,SDL_atof,(const char *a),(a),return)
 SDL_DYNAPI_PROC(int,SDL_atoi,(const char *a),(a),return)
-SDL_DYNAPI_PROC(void*,SDL_bsearch,(const void *a, const void *b, size_t c, size_t d, int (SDLCALL *e)(const void *, const void *)),(a,b,c,d,e),return)
-SDL_DYNAPI_PROC(void*,SDL_bsearch_r,(const void *a, const void *b, size_t c, size_t d, int (SDLCALL *e)(void *, const void *, const void *), void *f),(a,b,c,d,e,f),return)
+SDL_DYNAPI_PROC(void*,SDL_bsearch,(const void *a, const void *b, size_t c, size_t d, SDL_CompareCallback e),(a,b,c,d,e),return)
+SDL_DYNAPI_PROC(void*,SDL_bsearch_r,(const void *a, const void *b, size_t c, size_t d, SDL_CompareCallback_r e, void *f),(a,b,c,d,e,f),return)
 SDL_DYNAPI_PROC(void*,SDL_calloc,(size_t a, size_t b),(a,b),return)
 SDL_DYNAPI_PROC(double,SDL_ceil,(double a),(a),return)
 SDL_DYNAPI_PROC(float,SDL_ceilf,(float a),(a),return)
@@ -985,8 +985,8 @@ SDL_DYNAPI_PROC(double,SDL_modf,(double a, double *b),(a,b),return)
 SDL_DYNAPI_PROC(float,SDL_modff,(float a, float *b),(a,b),return)
 SDL_DYNAPI_PROC(double,SDL_pow,(double a, double b),(a,b),return)
 SDL_DYNAPI_PROC(float,SDL_powf,(float a, float b),(a,b),return)
-SDL_DYNAPI_PROC(void,SDL_qsort,(void *a, size_t b, size_t c, int (SDLCALL *d)(const void *, const void *)),(a,b,c,d),)
-SDL_DYNAPI_PROC(void,SDL_qsort_r,(void *a, size_t b, size_t c, int (SDLCALL *d)(void *, const void *, const void *), void *e),(a,b,c,d,e),)
+SDL_DYNAPI_PROC(void,SDL_qsort,(void *a, size_t b, size_t c, SDL_CompareCallback d),(a,b,c,d),)
+SDL_DYNAPI_PROC(void,SDL_qsort_r,(void *a, size_t b, size_t c, SDL_CompareCallback_r d, void *e),(a,b,c,d,e),)
 SDL_DYNAPI_PROC(void*,SDL_realloc,(void *a, size_t b),(a,b),return)
 SDL_DYNAPI_PROC(double,SDL_round,(double a),(a),return)
 SDL_DYNAPI_PROC(float,SDL_roundf,(float a),(a),return)
diff --git a/src/stdlib/SDL_qsort.c b/src/stdlib/SDL_qsort.c
index 771712d203..20a8573f15 100644
--- a/src/stdlib/SDL_qsort.c
+++ b/src/stdlib/SDL_qsort.c
@@ -507,8 +507,8 @@ fprintf(stderr, "after partitioning first=#%lu last=#%lu\n", (first-(char*)base)
 
 /* ---------------------------------------------------------------------- */
 
-extern void SDL_qsort_r(void *base, size_t nmemb, size_t size,
-           int (SDLCALL * compare)(void *, const void *, const void *), void *userdata) {
+void SDL_qsort_r(void *base, size_t nmemb, size_t size,
+           SDL_CompareCallback_r compare, void *userdata) {
 
   if (nmemb<=1) return;
   if (((size_t)base|size)&(WORD_BYTES-1))
@@ -525,7 +525,7 @@ static int SDLCALL qsort_non_r_bridge(void *userdata, const void *a, const void
     return compare(a, b);
 }
 
-void SDL_qsort(void *base, size_t nmemb, size_t size, int (SDLCALL *compare) (const void *, const void *))
+void SDL_qsort(void *base, size_t nmemb, size_t size, SDL_CompareCallback compare)
 {
     SDL_qsort_r(base, nmemb, size, qsort_non_r_bridge, compare);
 }
@@ -533,7 +533,7 @@ void SDL_qsort(void *base, size_t nmemb, size_t size, int (SDLCALL *compare) (co
 // Don't use the C runtime for such a simple function, since we want to allow SDLCALL callbacks and userdata.
 // SDL's replacement: Taken from the Public Domain C Library (PDCLib):
 // Permission is granted to use, modify, and / or redistribute at will.
-void *SDL_bsearch_r(const void *key, const void *base, size_t nmemb, size_t size, int (SDLCALL *compare)(void *, const void *, const void *), void *userdata)
+void *SDL_bsearch_r(const void *key, const void *base, size_t nmemb, size_t size, SDL_CompareCallback_r compare, void *userdata)
 {
     const void *pivot;
     size_t corr;
@@ -558,7 +558,7 @@ void *SDL_bsearch_r(const void *key, const void *base, size_t nmemb, size_t size
     return NULL;
 }
 
-void *SDL_bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (SDLCALL *compare)(const void *, const void *))
+void *SDL_bsearch(const void *key, const void *base, size_t nmemb, size_t size, SDL_CompareCallback compare)
 {
     // qsort_non_r_bridge just happens to match calling conventions, so reuse it.
     return SDL_bsearch_r(key, base, nmemb, size, qsort_non_r_bridge, compare);
diff --git a/src/thread/SDL_thread.c b/src/thread/SDL_thread.c
index 909dc78295..1589a56ad5 100644
--- a/src/thread/SDL_thread.c
+++ b/src/thread/SDL_thread.c
@@ -43,7 +43,7 @@ void *SDL_GetTLS(SDL_TLSID id)
     return storage->array[id - 1].data;
 }
 
-int SDL_SetTLS(SDL_TLSID id, const void *value, void(SDLCALL *destructor)(void *))
+int SDL_SetTLS(SDL_TLSID id, const void *value, SDL_TLSDestructorCallback destructor)
 {
     SDL_TLSData *storage;