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Fix failing test malloc/tst-interpose-nothread with GCC 7.

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The test malloc/tst-interpose-nothread fails on s390x if built
with GCC 7 and glibc commit "Remove the str(n)dup inlines
from string/bits/string2.h. Although inlining"
(ae65d4f3c3) with output:
error: free: 0x3fffdffa010: invalid allocation index: 0 (not less than 0)

The destructor check_for_allocations in malloc/tst-interpose-aux.c is
called twice.  One time after the test-child-process has finished successfully
and once after the test-parent-process finishes.
During the latter invocation, allocation_index == 0.  GCC 7 is now inlining the
free function and calls unconditionally fail in get_header as
header->allocation_index (type == size_t) is always >= allocation_index (= 0).
Before the mentioned commit above, strdup was replaced by strlen, malloc and
memcpy.  The malloc call was also inlined and allocation_index was set to one.

This patch moves the already existing compiler barrier before the invocation
of free.

ChangeLog:

	* malloc/tst-interpose-aux.c (check_for_allocations):
	Move compiler barrier before free.
This commit is contained in:
Stefan Liebler 2017-03-21 16:41:56 +01:00
parent 76b2c32a16
commit e4e26210c3
2 changed files with 6 additions and 1 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2017-03-21 Stefan Liebler <stli@linux.vnet.ibm.com>
* malloc/tst-interpose-aux.c (check_for_allocations):
Move compiler barrier before free.
2017-03-20 Joseph Myers <joseph@codesourcery.com>
[BZ #21279]

2
malloc/tst-interpose-aux.c
View File

@ -113,11 +113,11 @@ check_for_allocations (void)
{
/* Make sure that malloc is called at least once from libc. */
void *volatile ptr = strdup ("ptr");
free (ptr);
/* Compiler barrier. The strdup function calls malloc, which
updates allocation_index, but strdup is marked __THROW, so
the compiler could optimize away the reload. */
__asm__ volatile ("" ::: "memory");
free (ptr);
/* If the allocation count is still zero, it means we did not
interpose malloc successfully. */
if (allocation_index == 0)