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testsuite, mi: avoid a clang bug in 'user-selected-context-sync.exp'

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This test causes several timeouts for Clang, taking too long time to
finish.  The reason is, for an infinite loop of the form

   while(1); /* suppose this is line 30.  */

Clang generates code that looks like

   0x00000000004004d4 <+4>:     jmp    0x4004d9 <loop+9>
   0x00000000004004d9 <+9>:     jmp    0x4004d9 <loop+9>

So, the real loop is the instruction at address 0x4004d9.  But a
breakpoint that's defined at the loop line (assume line 30 in this
case) is inserted at address 0x4004d4.

  (gdb) break 30
  Breakpoint 1 at 0x4004d4: file test.c, line 30.

Therefore, continuing a thread that was spinning on the loop does not hit
the breakpoint.  The bug is reported at

  https://bugs.llvm.org/show_bug.cgi?id=49614

Tweak the infinite loop to spin on a variable to avoid this bug.  The
test is unrelated to the bug.

gdb/testsuite/ChangeLog:
2021-03-29  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* gdb.mi/user-selected-context-sync.exp: Spin on a variable in
	the infinite loop to avoid a Clang bug.
This commit is contained in:
Tankut Baris Aktemur 2021-03-29 16:00:41 +02:00
parent 25b48839b3
commit aa33ea6833
2 changed files with 13 additions and 2 deletions
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5
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2021-03-29 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdb.mi/user-selected-context-sync.exp: Spin on a variable in
the infinite loop to avoid a Clang bug.
2021-03-26 Will Schmidt <will_schmidt@vnet.ibm.com>
* gdb.arch/powerpc-disassembler-options.exp: Extend some test

10
gdb/testsuite/gdb.mi/user-selected-context-sync.c
View File

@ -27,7 +27,10 @@ static pthread_barrier_t barrier;
static void
child_sub_function (void)
{
while (1); /* thread loop line */
/* Deliberately spin on a variable instead of plain 'while (1)' to
avoid the Clang bug https://bugs.llvm.org/show_bug.cgi?id=49614. */
int spin = 1;
while (spin); /* thread loop line */
}
static void *
@ -57,7 +60,10 @@ main (void)
pthread_barrier_wait (&barrier);
while (1); /* main break line */
/* Deliberately spin on a variable instead of plain 'while (1)' to
avoid the Clang bug https://bugs.llvm.org/show_bug.cgi?id=49614. */
int spin = 1;
while (spin); /* main break line */
return 0;
}