mbedtls/platform.h: Avoid potential macro redefinition warnings.

Some identifiers (e.g. mbedtls_free) can name either functions or
macros depending on configuration settings.  For those that turn out
to name macros, first clear out any existing macro definitions to
accommodate possible unconditional bulk symbol renaming.  (There
remains no standard provision for such renaming, but it's nevertheless
straightforward enough to do as desired, particularly with this change
in place.)

Signed-off-by: Aaron M. Ucko <[email protected]>

include/mbedtls/platform.h

@@ -144,6 +144,8 @@ extern "C" {
 #if defined(MBEDTLS_PLATFORM_MEMORY)
 #if defined(MBEDTLS_PLATFORM_FREE_MACRO) && \
     defined(MBEDTLS_PLATFORM_CALLOC_MACRO)
+#undef mbedtls_free
+#undef mbedtls_calloc
 #define mbedtls_free       MBEDTLS_PLATFORM_FREE_MACRO
 #define mbedtls_calloc     MBEDTLS_PLATFORM_CALLOC_MACRO
 #else
@@ -165,6 +167,8 @@ int mbedtls_platform_set_calloc_free(void *(*calloc_func)(size_t, size_t),
                                      void (*free_func)(void *));
 #endif /* MBEDTLS_PLATFORM_FREE_MACRO && MBEDTLS_PLATFORM_CALLOC_MACRO */
 #else /* !MBEDTLS_PLATFORM_MEMORY */
+#undef mbedtls_free
+#undef mbedtls_calloc
 #define mbedtls_free       free
 #define mbedtls_calloc     calloc
 #endif /* MBEDTLS_PLATFORM_MEMORY && !MBEDTLS_PLATFORM_{FREE,CALLOC}_MACRO */
@@ -189,6 +193,7 @@ extern int (*mbedtls_fprintf)(FILE *stream, const char *format, ...);
 int mbedtls_platform_set_fprintf(int (*fprintf_func)(FILE *stream, const char *,
                                                      ...));
 #else
+#undef mbedtls_fprintf
 #if defined(MBEDTLS_PLATFORM_FPRINTF_MACRO)
 #define mbedtls_fprintf    MBEDTLS_PLATFORM_FPRINTF_MACRO
 #else
@@ -213,6 +218,7 @@ extern int (*mbedtls_printf)(const char *format, ...);
  */
 int mbedtls_platform_set_printf(int (*printf_func)(const char *, ...));
 #else /* !MBEDTLS_PLATFORM_PRINTF_ALT */
+#undef mbedtls_printf
 #if defined(MBEDTLS_PLATFORM_PRINTF_MACRO)
 #define mbedtls_printf     MBEDTLS_PLATFORM_PRINTF_MACRO
 #else
@@ -248,6 +254,7 @@ extern int (*mbedtls_snprintf)(char *s, size_t n, const char *format, ...);
 int mbedtls_platform_set_snprintf(int (*snprintf_func)(char *s, size_t n,
                                                        const char *format, ...));
 #else /* MBEDTLS_PLATFORM_SNPRINTF_ALT */
+#undef mbedtls_snprintf
 #if defined(MBEDTLS_PLATFORM_SNPRINTF_MACRO)
 #define mbedtls_snprintf   MBEDTLS_PLATFORM_SNPRINTF_MACRO
 #else
@@ -284,6 +291,7 @@ extern int (*mbedtls_vsnprintf)(char *s, size_t n, const char *format, va_list a
 int mbedtls_platform_set_vsnprintf(int (*vsnprintf_func)(char *s, size_t n,
                                                          const char *format, va_list arg));
 #else /* MBEDTLS_PLATFORM_VSNPRINTF_ALT */
+#undef mbedtls_vsnprintf
 #if defined(MBEDTLS_PLATFORM_VSNPRINTF_MACRO)
 #define mbedtls_vsnprintf   MBEDTLS_PLATFORM_VSNPRINTF_MACRO
 #else
@@ -308,6 +316,7 @@ extern void (*mbedtls_exit)(int status);
  */
 int mbedtls_platform_set_exit(void (*exit_func)(int status));
 #else
+#undef mbedtls_exit
 #if defined(MBEDTLS_PLATFORM_EXIT_MACRO)
 #define mbedtls_exit   MBEDTLS_PLATFORM_EXIT_MACRO
 #else
@@ -360,6 +369,8 @@ int mbedtls_platform_set_nv_seed(
     int (*nv_seed_write_func)(unsigned char *buf, size_t buf_len)
     );
 #else
+#undef mbedtls_nv_seed_read
+#undef mbedtls_nv_seed_write
 #if defined(MBEDTLS_PLATFORM_NV_SEED_READ_MACRO) && \
     defined(MBEDTLS_PLATFORM_NV_SEED_WRITE_MACRO)
 #define mbedtls_nv_seed_read    MBEDTLS_PLATFORM_NV_SEED_READ_MACRO