From mboxrd@z Thu Jan 1 00:00:00 1970 From: mathieu.desnoyers@efficios.com (Mathieu Desnoyers) Date: Mon, 18 Jun 2012 10:11:56 -0400 Subject: [lttng-dev] lttng-ust with --std=c99 -pedantic In-Reply-To: <4FDF1AC2.3070009@toojays.net> References: <20120612153257.GB14189@Krystal> <20120612155539.GA15859@Krystal> <4FDF1AC2.3070009@toojays.net> Message-ID: <20120618141156.GB6865@Krystal> * John Steele Scott (toojays at toojays.net) wrote: > On 13/06/12 01:25, Mathieu Desnoyers wrote: > > * Mathieu Desnoyers (mathieu.desnoyers at efficios.com) wrote: > >> Hi John, > >> > >> * John Steele Scott (toojays at toojays.net) wrote: > >>> I want to add lttng-ust tracepoints to a program which builds with "--std=c99 -pedantic". Right now this does not work. > >>> > >>> Using the demo program as an example, if you enable --std=c99, the first issue looks like: > >>> > >>> jscott at saaz:~/src/lttng-ust/tests/demo$ ccache gcc -std=c99 -DHAVE_CONFIG_H -I. -I../.. -I../../include/lttng -I../../include -Wall -g -O2 -MT demo.o -MD -MP -MF .deps/demo.Tpo -c -o demo.o demo.c > >>> In file included from demo.c:34:0: > >>> ust_tests_demo.h: In function ?__tracepoint_cb_ust_tests_demo___starting?: > >>> ust_tests_demo.h:27:23: warning: implicit declaration of function ?typeof? [-Wimplicit-function-declaration] > >>> ust_tests_demo.h:27:218: error: expected ?;? before ?_________p1? > >>> ust_tests_demo.h:27:395: error: ?_________p1? undeclared (first use in this function) > >>> ust_tests_demo.h:27:395: note: each undeclared identifier is reported only once for each function it appears in > >>> In file included from demo.c:34:0: > >>> ust_tests_demo.h: In function ?__tracepoint_cb_ust_tests_demo___done?: > >>> ust_tests_demo.h:35:214: error: expected ?;? before ?_________p1? > >>> ust_tests_demo.h:35:383: error: ?_________p1? undeclared (first use in this function) > >>> In file included from demo.c:35:0: > >>> ust_tests_demo2.h: In function ?__tracepoint_cb_ust_tests_demo2___loop?: > >>> ust_tests_demo2.h:27:299: error: expected ?;? before ?_________p1? > >>> ust_tests_demo2.h:27:470: error: ?_________p1? undeclared (first use in this function) > >>> In file included from demo.c:36:0: > >>> ust_tests_demo3.h: In function ?__tracepoint_cb_ust_tests_demo3___done?: > >>> ust_tests_demo3.h:27:215: error: expected ?;? before ?_________p1? > >>> ust_tests_demo3.h:27:386: error: ?_________p1? undeclared (first use in this function) > >>> > >>> This can be easily resolved by using __typeof__() instead of typeof(). Then I can build with --std=c99. But adding -pedantic still fails: > >> I pushed a fix for this: > >> > >> commit 6423c3134bf07d4a7db56f69f2c79b540a79c4f1 > >> Author: Mathieu Desnoyers > >> Date: Mon Jun 11 10:15:25 2012 -0400 > >> > >> Fix c99 compatibility: use __typeof__ instead of typeof in public headers > >> > >> Reported-by: John Steele Scott > >> Signed-off-by: Mathieu Desnoyers > >> > >> I also had issues with (void) arg parameters with tracepoints, so > >> pushed: > >> > >> commit 4495dd39c05739d0fb2bc463b7c093d2459ce2b6 > >> Author: Mathieu Desnoyers > >> Date: Tue Jun 12 11:22:46 2012 -0400 > >> > >> Fix: support -std=c99 in tracepoint macros > >> > >> Signed-off-by: Mathieu Desnoyers > >> > >> I had also to fix userspace RCU library, with: > >> > >> > >> commit e51500edbd9919cee53bc85cbb4b22cd4786fc42 > >> Author: Mathieu Desnoyers > >> Date: Tue Jun 12 11:24:31 2012 -0400 > >> > >> Fix c99 compatibility: use __asm__ and __volatile__ in public headers > >> > >> Signed-off-by: Mathieu Desnoyers > >> > >> commit bdffa73aa208ad5f1e5b3a3cb6cbf86ac6996559 > >> Author: Mathieu Desnoyers > >> Date: Mon Jun 11 10:16:35 2012 -0400 > >> > >> Fix c99 compatibility: use __typeof__ instead of typeof in public headers > >> > >> Reported-by: John Steele Scott > >> Signed-off-by: Mathieu Desnoyers > >> > >> > >>> jscott at saaz:~/src/lttng-ust/tests/demo$ ccache gcc -std=c99 -Dtypeof=__typeof__ -pedantic -DHAVE_CONFIG_H -I. -I../.. -I../../include/lttng -I../../include -Wall -g -O2 -MT demo.o -MD -MP -MF .deps/demo.Tpo -c -o demo.o demo.c > >>> In file included from ust_tests_demo.h:25:0, > >>> from demo.c:34: > >>> ../../include/lttng/tracepoint.h: In function ?__tracepoints__init?: > >>> ../../include/lttng/tracepoint.h:251:4: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> ../../include/lttng/tracepoint.h:255:4: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> ../../include/lttng/tracepoint.h:260:4: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> ../../include/lttng/tracepoint.h:264:4: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> ../../include/lttng/tracepoint.h:268:4: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> In file included from demo.c:34:0: > >>> ust_tests_demo.h: In function ?__tracepoint_cb_ust_tests_demo___starting?: > >>> ust_tests_demo.h:27:161: warning: ISO C forbids braced-groups within expressions [-pedantic] > >>> ust_tests_demo.h:27:549: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> In file included from demo.c:34:0: > >>> ust_tests_demo.h: In function ?__tracepoint_cb_ust_tests_demo___done?: > >>> ust_tests_demo.h:35:161: warning: ISO C forbids braced-groups within expressions [-pedantic] > >>> ust_tests_demo.h:35:537: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> In file included from demo.c:35:0: > >>> ust_tests_demo2.h: In function ?__tracepoint_cb_ust_tests_demo2___loop?: > >>> ust_tests_demo2.h:27:245: warning: ISO C forbids braced-groups within expressions [-pedantic] > >>> ust_tests_demo2.h:27:624: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >>> In file included from demo.c:36:0: > >>> ust_tests_demo3.h: In function ?__tracepoint_cb_ust_tests_demo3___done?: > >>> ust_tests_demo3.h:27:161: warning: ISO C forbids braced-groups within expressions [-pedantic] > >>> ust_tests_demo3.h:27:540: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] > >> I see these warnings, the only thing that currently fails is due to > >> BYTE_ORDER and BIG_ENDIAN not being defined. By adding: > >> > >> -DBYTE_ORDER=__BYTE_ORDER -DBIG_ENDIAN=__BIG_ENDIAN > >> > >> my tests/hello program, with a Makefile.am modified to do: > >> > >> hello_CFLAGS = -Werror=old-style-definition --std=c99 -pedantic > >> > >> prints many pedantic warnings, and fails with: > >> > >> ././ust_tests_hello.h:55:1: error: zero or negative size array ?__event_fields___ust_tests_hello___tptest_sighandler? > >> > >> which seems to be caused by my event with 0 fields, which try to create > >> an array of length 0. > >> > >> I'll look into this one. > > Please try again with lttng-ust master HEAD, userspace-rcu master HEAD, > > and let me know if you experience problems compiling your instrumented > > application with --std=c99 -pedantic. Please note that the probe object > > (e.g. tp.c in the tests/hello program) needs to be compiled with gnu > > extensions, so you should not use --std=c99 for this specific object. > > Mathieu, > > Thanks for your reply, sorry it has taken me so long to respond. > > I can now build this application with userspace tracing. I was > actually able to compile the probe object with --std=c99 as well (this > time on Centos 6.2, didn't try yet on Ubuntu). Would you expect any > problems from this? I only have a single tracepoint in this app, but > it does seem to work. --std=c99 will not work to compile probes containing tracepoints taking 0 arguments. This is because c99 does not allow 0-sized arrays, and I don't want to complexify the probe generation to take care of this issue. > > The thing I forgot to mention is: okay, I can build now with > -pedantic, but I can't build with "-pedantic -Werror". This > application builds with "--std=c99 -pedantic -Werror" (among many > other flags). I can of course remove -Werror for my tests, but in the > longer term I would like to see lttng-ust enabled in our regular > build, and disabling -Werror for that is not something we want to do. > If I only had to disable it for the trace provider, I could negotiate > that, but disabling it for any module which uses tracepoints is > undesirable. > > I haven't yet looked at how difficult it would be do eliminate these > pedantic warnings. Do you have a feel for what is involved? > Preprocessor tricks warp my mind. :( I don't think we'll want to make the lttng probe module build under --std=c99 -pedandic -Werror, but I think we should focus on making sure the tracepoint part that is built within the application (with TRACEPOINT_CREATE_PROBES _not_ defined) builds fine in --std=c99 -pedantic. Currently, building a simple test program with tracepoints under --std=c99 -pedantic gets me: In file included from ust_tests_hello.h:25:0, from hello.c:34: ../../include/lttng/tracepoint.h: In function ?__tracepoints__init?: ../../include/lttng/tracepoint.h:261:3: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] ../../include/lttng/tracepoint.h:265:3: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] ../../include/lttng/tracepoint.h:270:3: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] ../../include/lttng/tracepoint.h:274:3: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] ../../include/lttng/tracepoint.h:278:3: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] ---> see include/lttng/tracepoint.h __tracepoints__init(): ----> This is caused by use of dlsym() to lookup a function pointer from a symbol. dlsym() returns "void *", and we cast it into function pointer type. Ideas on how to make this c99 pedantic compliant are welcome. ------------------ In file included from hello.c:34:0: ust_tests_hello.h: In function ?__tracepoint_cb_ust_tests_hello___tptest?: ust_tests_hello.h:28:1: warning: ISO C forbids braced-groups within expressions [-pedantic] ust_tests_hello.h:28:1: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] ust_tests_hello.h: In function ?__tracepoint_cb_ust_tests_hello___tptest_sighandler?: ust_tests_hello.h:52:1: warning: ISO C forbids braced-groups within expressions [-pedantic] ust_tests_hello.h:52:1: warning: ISO C forbids conversion of object pointer to function pointer type [-pedantic] ---> see include/lttng/tracepoint.h #define _DECLARE_TRACEPOINT(_provider, _name, ...) \ extern struct tracepoint __tracepoint_##_provider##___##_name; \ static inline void __tracepoint_cb_##_provider##___##_name(_TP_ARGS_PROTO(__VA_ARGS__)) \ [...] ----> this is caused by use of "tp_rcu_dereference_bp()", which is defined in include/lttng/tracepoint-rcu.h (in the #else clause) : #define tp_rcu_dereference_bp(p) \ ({ \ __typeof__(p) _________p1 = URCU_FORCE_CAST(__typeof__(p), \ tracepoint_dlopen.rcu_dereference_sym_bp(URCU_FORCE_CAST(void *, p))); \ (_________p1); \ }) For this one, we should be able to change it into a single-expression and remove the braced-groups, since we are just really evaluating a single expression here. Fixed by the following commit in lttng-ust master: commit a4eaf8eabe829be8f7d7432ffaf83291a068b0ed Author: Mathieu Desnoyers Date: Mon Jun 18 10:10:36 2012 -0400 Fix c99 compatibility: tp_rcu_dereference_bp() should not use braced-groups within expressions ------------------ hello.c: In function ?inthandler?: hello.c:39:47: warning: ISO C99 requires rest arguments to be used [enabled by default] ---> see include/lttng/tracepoint.h tracepoint() macro. ----> this is caused by not passing any argument to the tracepoint. Ideas on how to fix this are welcome, as I don't see any way to do it in C99-pedantic. Thanks! Mathieu > > cheers, > > John > > _______________________________________________ > lttng-dev mailing list > lttng-dev at lists.lttng.org > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com