Fix:
warning: inline function 'mmc_buffer_alloc' is not defined [-Wundefined-inline]
warning: inline function 'mmc_buffer_free' is not defined [-Wundefined-inline]
warning: inline function 'mmc_prepare_key' is not defined [-Wundefined-inline]
warning: inline function 'mmc_prepare_key_ex' is not defined [-Wundefined-inline]
warning: inline function 'mmc_queue_contains' is not defined [-Wundefined-inline]
warning: inline function 'mmc_queue_copy' is not defined [-Wundefined-inline]
warning: inline function 'mmc_queue_free' is not defined [-Wundefined-inline]
warning: inline function 'mmc_queue_pop' is not defined [-Wundefined-inline]
warning: inline function 'mmc_queue_push' is not defined [-Wundefined-inline]
warning: inline function 'mmc_queue_remove' is not defined [-Wundefined-inline]
Includes all of:
https://github.com/websupport-sk/pecl-memcache/commit/82480df30259a439a545a23daffb076a047ffc74
And part of:
https://github.com/websupport-sk/pecl-memcache/commit/c051ca73ee98a4e5207799ea452470153695512f
See also:
https://github.com/websupport-sk/pecl-memcache/issues/63
--- memcache_pool.c.orig	2013-04-07 21:12:54.000000000 -0500
+++ memcache_pool.c	2021-12-23 07:15:27.000000000 -0600
@@ -40,7 +40,7 @@
 
 ZEND_DECLARE_MODULE_GLOBALS(memcache)
 
-inline void mmc_buffer_alloc(mmc_buffer_t *buffer, unsigned int size)  /*
+MMC_POOL_INLINE void mmc_buffer_alloc(mmc_buffer_t *buffer, unsigned int size)  /*
 	ensures space for an additional size bytes {{{ */
 {
 	register size_t newlen;
@@ -48,7 +48,7 @@
 }
 /* }}} */
 
-inline void mmc_buffer_free(mmc_buffer_t *buffer)  /* {{{ */
+MMC_POOL_INLINE void mmc_buffer_free(mmc_buffer_t *buffer)  /* {{{ */
 {
 	if (buffer->value.c != NULL) {
 		smart_str_free(&(buffer->value));
@@ -1676,7 +1676,7 @@
 }
 /* }}} */
 
-inline int mmc_prepare_key_ex(const char *key, unsigned int key_len, char *result, unsigned int *result_len)  /* {{{ */
+MMC_POOL_INLINE int mmc_prepare_key_ex(const char *key, unsigned int key_len, char *result, unsigned int *result_len)  /* {{{ */
 {
 	unsigned int i;
 	if (key_len == 0) {
@@ -1694,7 +1694,7 @@
 }
 /* }}} */
 
-inline int mmc_prepare_key(zval *key, char *result, unsigned int *result_len)  /* {{{ */
+MMC_POOL_INLINE int mmc_prepare_key(zval *key, char *result, unsigned int *result_len)  /* {{{ */
 {
 	if (Z_TYPE_P(key) == IS_STRING) {
 		return mmc_prepare_key_ex(Z_STRVAL_P(key), Z_STRLEN_P(key), result, result_len);
--- memcache_pool.h.orig	2013-04-07 21:12:54.000000000 -0500
+++ memcache_pool.h	2021-12-23 07:15:30.000000000 -0600
@@ -135,8 +135,15 @@
 #define mmc_buffer_release(b) memset((b), 0, sizeof(*(b)))
 #define mmc_buffer_reset(b) (b)->value.len = (b)->idx = 0
 
-inline void mmc_buffer_alloc(mmc_buffer_t *, unsigned int);
-inline void mmc_buffer_free(mmc_buffer_t *);
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+/* see https://gcc.gnu.org/gcc-5/porting_to.html */
+#define MMC_POOL_INLINE extern inline
+#else
+#define MMC_POOL_INLINE inline
+#endif
+
+void mmc_buffer_alloc(mmc_buffer_t *, unsigned int);
+void mmc_buffer_free(mmc_buffer_t *);
 
 /* stream handlers */
 typedef struct mmc_stream mmc_stream_t;
@@ -391,8 +398,8 @@
 double timeval_to_double(struct timeval tv);
 struct timeval double_to_timeval(double sec);
 
-inline int mmc_prepare_key_ex(const char *, unsigned int, char *, unsigned int *);
-inline int mmc_prepare_key(zval *, char *, unsigned int *);
+int mmc_prepare_key_ex(const char *, unsigned int, char *, unsigned int *);
+int mmc_prepare_key(zval *, char *, unsigned int *);
 
 #define mmc_str_left(h, n, hlen, nlen) ((hlen) >= (nlen) ? memcmp((h), (n), (nlen)) == 0 : 0)
 
--- memcache_queue.h.orig	2013-04-07 21:12:54.000000000 -0500
+++ memcache_queue.h	2021-12-23 07:15:30.000000000 -0600
@@ -39,16 +39,19 @@
 
 #ifdef PHP_WIN32
 #define MMC_QUEUE_INLINE
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+/* see https://gcc.gnu.org/gcc-5/porting_to.html */
+#define MMC_QUEUE_INLINE extern inline
 #else
 #define MMC_QUEUE_INLINE inline
 #endif
 
-MMC_QUEUE_INLINE void mmc_queue_push(mmc_queue_t *, void *);
-MMC_QUEUE_INLINE void *mmc_queue_pop(mmc_queue_t *);
-MMC_QUEUE_INLINE int mmc_queue_contains(mmc_queue_t *, void *);
-MMC_QUEUE_INLINE void mmc_queue_free(mmc_queue_t *);
-MMC_QUEUE_INLINE void mmc_queue_copy(mmc_queue_t *, mmc_queue_t *);
-MMC_QUEUE_INLINE void mmc_queue_remove(mmc_queue_t *, void *);
+void mmc_queue_push(mmc_queue_t *, void *);
+void *mmc_queue_pop(mmc_queue_t *);
+int mmc_queue_contains(mmc_queue_t *, void *);
+void mmc_queue_free(mmc_queue_t *);
+void mmc_queue_copy(mmc_queue_t *, mmc_queue_t *);
+void mmc_queue_remove(mmc_queue_t *, void *);
 
 #endif /*MEMCACHE_QUEUE_H_*/