eliminate alloca(3) use

alloca(3) is difficult for the compiler and static checkers to
deal with, and we already reserve TSD space for storing path
names.

2 files changed, 13 insertions, 10 deletions

diff --git a/Mwrap.xs b/Mwrap.xs
index b515894..367a4c3 100644
--- a/Mwrap.xs
+++ b/Mwrap.xs
@@ -153,7 +153,7 @@ mwrap_get(loc)
 PREINIT:
         STRLEN len;
         const char *str;
-        struct src_loc *k = (void *)kbuf;
+        struct src_loc *k = &tsd.src_loc;
         uintptr_t p;
         struct cds_lfht_iter iter;
         struct cds_lfht_node *cur;
diff --git a/mwrap_core.h b/mwrap_core.h
index 3abc3dd..09b7930 100644
--- a/mwrap_core.h
+++ b/mwrap_core.h
@@ -178,9 +178,12 @@ struct alloc_hdr {
 };
 
 /* $PATHNAME:$LINENO */
-static MWRAP_TSD char kbuf[
-        sizeof(struct src_loc) + PATH_MAX + sizeof(":") + UINT2STR_MAX
-];
+static MWRAP_TSD union {
+        char kbuf[
+                sizeof(struct src_loc) + PATH_MAX + sizeof(":") + UINT2STR_MAX
+        ];
+        struct src_loc src_loc;
+} tsd;
 
 static struct alloc_hdr *ptr2hdr(void *p)
 {
@@ -290,7 +293,7 @@ static struct src_loc *assign_line(size_t size, const char *file, unsigned line)
         len = strlen(file);
         if (len > PATH_MAX)
                 len = PATH_MAX;
-        k = (void *)kbuf;
+        k = &tsd.src_loc;
         k->total = size;
         dst = mempcpy(k->k, file, len);
         *dst++ = ':';
@@ -311,7 +314,6 @@ static struct src_loc *
 update_stats_rcu_lock(size_t *generation, size_t size, uintptr_t caller)
 {
         struct src_loc *k, *ret = 0;
-        static const size_t xlen = sizeof(caller);
         struct cds_lfht *t = CMM_LOAD_SHARED(totals);
         const COP *cop = NULL;
 
@@ -326,11 +328,11 @@ update_stats_rcu_lock(size_t *generation, size_t size, uintptr_t caller)
                 ret = assign_line(size, OutCopFILE(cop), CopLINE(cop));
 #endif /* MWRAP_PERL */
         if (!ret) {
-                k = alloca(sizeof(*k) + xlen);
+                k = &tsd.src_loc;
                 k->total = size;
-                memcpy(k->k, &caller, xlen);
+                memcpy(k->k, &caller, sizeof(caller));
                 k->capa = 0;
-                hash_loc(k, xlen);
+                hash_loc(k, sizeof(caller));
                 ret = totals_add_rcu(k);
         }
 out:
@@ -672,7 +674,8 @@ static void dump_destructor(void)
                         *dump_path) {
                 char *end = strchr(dump_path, ',');
                 if (end) {
-                        char *tmp = alloca(end - dump_path + 1);
+                        char *tmp = tsd.kbuf;
+                        assert((end - dump_path) < sizeof(tsd.kbuf));
                         end = mempcpy(tmp, dump_path, end - dump_path);
                         *end = 0;
                         dump_path = tmp;