Tweak Makefile, asserts, comments.dj/malloc-tcache

* Un-Wundef-ify -DUSE_TCACHE
* More asserts in tcache get/put functions
* Clarify redundancy in tcache structure

2 files changed, 6 insertions, 2 deletions

diff --git a/malloc/Makefile b/malloc/Makefile
index dd8a43a..e6ca11c 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -169,7 +169,9 @@ tst-malloc-usable-tunables-ENV = GLIBC_TUNABLES=glibc.malloc.check=3
 tst-malloc-usable-static-tunables-ENV = $(tst-malloc-usable-tunables-ENV)
 
 ifeq ($(experimental-malloc),yes)
-CPPFLAGS-malloc.c += -DUSE_TCACHE
+CPPFLAGS-malloc.c += -DUSE_TCACHE=1
+else
+CPPFLAGS-malloc.c += -DUSE_TCACHE=0
 endif
 # Uncomment this for test releases.  For public releases it is too expensive.
 #CPPFLAGS-malloc.o += -DMALLOC_DEBUG=1
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 91551ae..d904db8 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2927,7 +2927,8 @@ typedef struct tcache_entry {
 /* There is one of these for each thread, which contains the
    per-thread cache (hence "tcache_perthread_struct").  Keeping
    overall size low is mildly important.  Note that COUNTS and ENTRIES
-   are redundant, this is for performance reasons.  */
+   are redundant (we could have just counted the linked list each
+   time), this is for performance reasons.  */
 typedef struct tcache_perthread_struct {
   char counts[TCACHE_MAX_BINS];
   tcache_entry *entries[TCACHE_MAX_BINS];
@@ -2955,6 +2956,7 @@ tcache_get (size_t tc_idx)
 {
   tcache_entry *e = tcache->entries[tc_idx];
   assert (tc_idx < TCACHE_MAX_BINS);
+  assert (tcache->entries[tc_idx] > 0);
   tcache->entries[tc_idx] = e->next;
   --(tcache->counts[tc_idx]);
   return (void *) e;