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[PATCH][BZ #16195] Fix build warnings from systemtap probes in non-systemtap configurations
- From: Siddhesh Poyarekar <siddhesh at redhat dot com>
- To: libc-alpha at sourceware dot org
- Cc: jsm28 at gcc dot gnu dot org
- Date: Mon, 2 Dec 2013 20:02:50 +0530
- Subject: [PATCH][BZ #16195] Fix build warnings from systemtap probes in non-systemtap configurations
- Authentication-results: sourceware.org; auth=none
Hi,
Joseph pointed out in the bug report (and in an earlier thread) that
systemtap probes cause build time warnings like the following:
../sysdeps/ieee754/dbl-64/e_atan2.c:602:4: warning: the address of 'p'
will always evaluate as 'true' [-Waddress]
due to the fact that we're now passing non-weak variables to
LIBC_PROBE in the libm probes. This happens only on configurations
that do not enable systemtap. The macro definition of LIBC_PROBE in
this case only acts as a sanity checker to ensure that the number
parameters passed to LIBC_PROBE is equal to the argument count
parameter passed before it. This can be done in a much simpler manner
by just adding a macro definition for each number of arguments. I am
assuming here that we don't really want to bother with supporting
LIBC_PROBE with an indeterminate number of arguments and if there is a
need for a probe to have more data than what is currently supported (4
arguments), one could simply add an additional macro here.
Tested that it gets rid of the warning on i686 and also verified that
nothing changed on x86_64. OK to commit?
Siddhesh
[BZ #16195]
* include/stap-probe.h [!USE_STAP_PROBE && !__ASSEMBLER__]
(LIBC_PROBE): Change definition to call STAP_PROBE* macros.
(STAP_PROBE0): New macro.
(STAP_PROBE1): Likewise.
(STAP_PROBE2): Likewise.
(STAP_PROBE3): Likewise.
(STAP_PROBE4): Likewise.
diff --git a/include/stap-probe.h b/include/stap-probe.h
index 5f72556..e296350 100644
--- a/include/stap-probe.h
+++ b/include/stap-probe.h
@@ -61,13 +61,14 @@
# ifndef __ASSEMBLER__
/* Evaluate all the arguments and verify that N matches their number. */
-# define LIBC_PROBE(name, n, ...) \
- do { \
- _Bool __libc_probe_args[] = { 0, ## __VA_ARGS__ }; \
- _Bool __libc_probe_verify_n[(sizeof __libc_probe_args / sizeof (_Bool)) \
- == n + 1 ? 1 : -1]; \
- (void) __libc_probe_verify_n; \
- } while (0)
+#define LIBC_PROBE(name, n, ...) STAP_PROBE##n (__VA_ARGS__)
+
+#define STAP_PROBE0()
+#define STAP_PROBE1(a1)
+#define STAP_PROBE2(a1, a2)
+#define STAP_PROBE3(a1, a2, a3)
+#define STAP_PROBE4(a1, a2, a3, a4)
+
# else
# define LIBC_PROBE(name, n, ...) /* Nothing. */
# endif