[lttng-dev] lttng-ust with --std=c99 -pedantic

Tue Jun 12 11:32:57 EDT 2012

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 <mathieu.desnoyers at efficios.com>
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 <toojays at toojays.net>
    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

I also had issues with (void) arg parameters with tracepoints, so
pushed:

commit 4495dd39c05739d0fb2bc463b7c093d2459ce2b6
Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Date:   Tue Jun 12 11:22:46 2012 -0400

    Fix: support -std=c99 in tracepoint macros

    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

I had also to fix userspace RCU library, with:

commit e51500edbd9919cee53bc85cbb4b22cd4786fc42
Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Date:   Tue Jun 12 11:24:31 2012 -0400

    Fix c99 compatibility: use __asm__ and __volatile__ in public headers

    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

commit bdffa73aa208ad5f1e5b3a3cb6cbf86ac6996559
Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
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 <toojays at toojays.net>
    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

> 
> 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.

Thanks,

Mathieu

> 
> This is with 4.6.1-9ubuntu3 on Ubuntu 11.10, lttng-ust master 5a821c.
> 
> Would it be particularly difficult to make the lttng-ust tracepoints compatible with programs built with -pedantic?
> 
> cheers,
> 
> John
> 
> 
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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com