NimBLE: Fix misc warnings and return code in ble_hs_tx_data

- Previously `ble_hs_tx_data` returned 0 irrespective of error code returned by
  `ble_hci_trans_hs_acl_tx`.
- Minor changes in `porting/nimble/` and `ble_gattc.c` to remove discard const
  qualifier warnings, fixes #4028.

porting/nimble/include/mem/mem.h

@@ -42,7 +42,7 @@ int mem_malloc_mbufpkt_pool(struct os_mempool *mempool,
                             void **out_buf);
 int mem_init_mbuf_pool(void *mem, struct os_mempool *mempool,
                        struct os_mbuf_pool *mbuf_pool, int num_blocks,
-                       int block_size, char *name);
+                       int block_size, const char *name);
 
 /**
  * Specifies a function used as a callback.  Functions of this type allocate an

porting/nimble/include/os/os.h

@@ -26,6 +26,18 @@
 extern "C" {
 #endif
 
+#if !defined __cplusplus
+#define static_assert _Static_assert
+#endif
+
+#ifndef min
+#define min(a, b) ((a)<(b)?(a):(b))
+#endif
+
+#ifndef max
+#define max(a, b) ((a)>(b)?(a):(b))
+#endif
+
 #include "syscfg/syscfg.h"
 #include "nimble/nimble_npl.h"
 

porting/nimble/include/os/os_mempool.h

@@ -70,7 +70,7 @@ struct os_mempool {
     STAILQ_ENTRY(os_mempool) mp_list;
     SLIST_HEAD(,os_memblock);
     /** Name for memory block */
-    char *name;
+    const char *name;
 };
 
 /**
@@ -182,7 +182,7 @@ typedef __uint128_t os_membuf_t;
  * @return os_error_t
  */
 os_error_t os_mempool_init(struct os_mempool *mp, uint16_t blocks,
-                           uint32_t block_size, void *membuf, char *name);
+                           uint32_t block_size, void *membuf, const char *name);
 
 /**
  * Initializes an extended memory pool.  Extended attributes (e.g., callbacks)
@@ -198,7 +198,7 @@ os_error_t os_mempool_init(struct os_mempool *mp, uint16_t blocks,
  * @return os_error_t
  */
 os_error_t os_mempool_ext_init(struct os_mempool_ext *mpe, uint16_t blocks,
-                               uint32_t block_size, void *membuf, char *name);
+                               uint32_t block_size, void *membuf, const char *name);
 
 /**
  * Removes the specified mempool from the list of initialized mempools.

porting/nimble/include/stats/stats.h

@@ -67,7 +67,7 @@ stats_register(void *a, void *b)
 }
 
 static inline int
-stats_init_and_reg(void *a, uint8_t b, uint8_t c, void *d, uint8_t e, void *f)
+stats_init_and_reg(void *a, uint8_t b, uint8_t c, void *d, uint8_t e, const char *f)
 {
     /* dummy */
     return 0;

porting/nimble/src/mem.c

@@ -206,7 +206,7 @@ mem_malloc_mbufpkt_pool(struct os_mempool *mempool,
 int
 mem_init_mbuf_pool(void *mem, struct os_mempool *mempool,
                    struct os_mbuf_pool *mbuf_pool, int num_blocks,
-                   int block_size, char *name)
+                   int block_size, const char *name)
 {
     int rc;
 

porting/nimble/src/os_mempool.c

@@ -38,7 +38,7 @@
 #define OS_MEMPOOL_TRUE_BLOCK_SIZE(mp) OS_MEM_TRUE_BLOCK_SIZE(mp->mp_block_size)
 #endif
 
-STAILQ_HEAD(, os_mempool) g_os_mempool_list;
+STAILQ_HEAD(, os_mempool) g_os_mempool_list = STAILQ_HEAD_INITIALIZER(g_os_mempool_list);
 
 #if MYNEWT_VAL(OS_MEMPOOL_POISON)
 static uint32_t os_mem_poison = 0xde7ec7ed;
@@ -118,7 +118,7 @@ os_mempool_guard_check(const struct os_mempool *mp, void *start)
 
 static os_error_t
 os_mempool_init_internal(struct os_mempool *mp, uint16_t blocks,
-                         uint32_t block_size, void *membuf, char *name,
+                         uint32_t block_size, void *membuf, const char *name,
                          uint8_t flags)
 {
     int true_block_size;
@@ -181,14 +181,14 @@ os_mempool_init_internal(struct os_mempool *mp, uint16_t blocks,
 
 os_error_t
 os_mempool_init(struct os_mempool *mp, uint16_t blocks, uint32_t block_size,
-                void *membuf, char *name)
+                void *membuf, const char *name)
 {
     return os_mempool_init_internal(mp, blocks, block_size, membuf, name, 0);
 }
 
 os_error_t
 os_mempool_ext_init(struct os_mempool_ext *mpe, uint16_t blocks,
-                    uint32_t block_size, void *membuf, char *name)
+                    uint32_t block_size, void *membuf, const char *name)
 {
     int rc;
 

porting/nimble/src/os_msys_init.c

@@ -106,7 +106,7 @@ os_msys_sanity(struct os_sanity_check *sc, void *arg)
 static void
 os_msys_init_once(void *data, struct os_mempool *mempool,
                   struct os_mbuf_pool *mbuf_pool,
-                  int block_count, int block_size, char *name)
+                  int block_count, int block_size, const char *name)
 {
     int rc;