glibc.git/malloc, branch master

malloc: Use _int_free_chunk in tcache_thread_shutdown

2025-11-20T12:28:46+00:00

Directly call _int_free_chunk during tcache shutdown to avoid recursion.
Calling __libc_free on a block from tcache gets flagged as a double free,
and tcache_double_free_verify checks every tcache chunk (quadratic
overhead).

Reviewed-by: Arjun Shankar

malloc: add free_sized and free_aligned_sized from C23

2025-11-19T16:47:53+00:00

Signed-off-by: Justin King 
Reviewed-by: Adhemerval Zanella

malloc: Simplify tst-free-errno munmap failure test

2025-11-18T13:28:42+00:00

The Linux specific test-case in tst-free-errno was backing up malloc
metadata for a large mmap'd block, overwriting the block with its own
mmap, then restoring malloc metadata and calling free to force an munmap
failure.  However, the backed up pages containing metadata can
occasionally be overlapped by the overwriting mmap, leading to a
metadata corruption.

This commit replaces this Linux specific test case with a simpler,
generic, three block allocation, expecting the kernel to coalesce the
VMAs, then cause a fragmentation to trigger the same failure.

Reviewed-by: Florian Weimer

Cleanup some recently added whitespace.

2025-10-31T01:56:58+00:00

Reviewed-by: H.J. Lu

Annotate swtich fall-through

2025-10-29T15:54:01+00:00

The clang default to warning for missing fall-through and it does
not support all comment-like annotation that gcc does.  Use C23
[[fallthrough]] annotation instead.
proper attribute instead.

Reviewed-by: Collin Funk

malloc: Remove unused tcache_set_inactive

2025-10-29T15:53:53+00:00

clang warns that this function is not used.

Reviewed-by: H.J. Lu

malloc: fix large tcache code to check for exact size match

2025-10-24T16:55:02+00:00

The tcache is used for allocation only if an exact match is found. In the
large tcache code added in commit cbfd7988107b, we currently extract a
chunk of size greater than or equal to the size we need, but don't check
strict equality. This patch fixes that behaviour.

Reviewed-by: Wilco Dijkstra

malloc: avoid need for tcache == NULL checks

2025-10-21T20:51:03+00:00

Avoid needing to check for tcache == NULL by initializing it
to a dummy read-only tcache structure.  This dummy is all zeros,
so logically it is both full (when you want to put) and empty (when
you want to get).  Also, there are two dummies, one used for
"not yet initialized" and one for "tunables say we shouldn't have
a tcache".

The net result is twofold:

1. Checks for tcache == NULL may be removed from the fast path.
    Whether this makes the fast path faster when tcache is
    disabled is TBD, but the normal case is tcache enabled.

2. no memory for tcache is allocated if tunables disable caching.

Co-authored-by: Florian Weimer 
Reviewed-by: Wilco Dijkstra

Suppress -Wmaybe-uninitialized only for gcc

2025-10-21T12:24:05+00:00

The warning is not supported by clang.

Reviewed-by: Sam James

malloc: Do not call madvise if heap's oldsize >= THP size

2025-10-20T14:33:54+00:00

Linux handles virtual memory in Virtual Memory Areas (VMAs). The
madvise(MADV_HUGEPAGE) call works on a VMA granularity, which sets the
VM_HUGEPAGE flag on the VMA. This flag is invariant of the mprotect()
syscall which is used in growing the secondary heaps. Therefore, we
need to call madvise() only when we are sure that VM_HUGEPAGE was not
previously set, which is only in the case when h->size < mp_.thp_pagesize.

Reviewed-by: Adhemerval Zanella