From de895ddcd7fc45caeeeb0ae312311b8bd31d82c5 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Wed, 12 Jul 2017 10:53:13 +0100 Subject: Disable single thread optimization for open_memstream Single thread optimization is valid if at thread creation time the optimization can be disabled. This is in principle true for all stream objects that user code can access (and thus needs locking), using the same internal list as fflush(0) uses. However in glibc open_memstream is not on that list (BZ 21735) so the optimization has to be disabled. * libio/memstream.c (__open_memstream): Set _IO_FLAGS2_NEED_LOCK. * libio/wmemstream.c (open_wmemstream): Likewise. * nptl/tst-memstream.c: New. --- libio/memstream.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'libio/memstream.c') diff --git a/libio/memstream.c b/libio/memstream.c index f83d4a5213..e391efd48a 100644 --- a/libio/memstream.c +++ b/libio/memstream.c @@ -96,6 +96,9 @@ __open_memstream (char **bufloc, _IO_size_t *sizeloc) new_f->fp.bufloc = bufloc; new_f->fp.sizeloc = sizeloc; + /* Disable single thread optimization. BZ 21735. */ + new_f->fp._sf._sbf._f._flags2 |= _IO_FLAGS2_NEED_LOCK; + return (_IO_FILE *) &new_f->fp._sf._sbf; } libc_hidden_def (__open_memstream) -- cgit v1.2.3