[asterisk-dev] [Code Review] 4533: clang compiler warning: -Wtautological-compare

rmudgett reviewboard at asterisk.org
Tue Mar 31 21:44:58 CDT 2015 


> On March 31, 2015, 8:16 p.m., rmudgett wrote:
> > /branches/13/funcs/func_curl.c, lines 174-175
> > <https://reviewboard.asterisk.org/r/4533/diff/7/?file=73369#file73369line174>
> >
> >     Try defining this as:
> >     #define CURLOPT_SPECIAL_HASHCOMPAT ((CURLoption) -500)
> >     
> >     This should shut-up the compiler without changing the binary value.
> 
> Diederik de Groot wrote:
>     CurlOption is a positive enum though. So the warning about it not being allowed to be negative remains, won't it ?
>     
>     BTW: I made a typo while changing this one
>     I was meaning to set it to:
>     #define CURLOPT_SPECIAL_HASHCOMPAT CURLOPT_LASTENTRY
>     Which is a legal value. Not really happy with this though.
>     
>     Setting it to 
>     #define CURLOPT_SPECIAL_HASHCOMPAT ((CURLoption) 500)
>     Might be an option, not sure if this is checked though.
>     
>     This would require a little further source investigation.
>

The cast should shut the compiler up as you are telling the compiler to reinterpret the -500 to be a member of the enum.  If not then it's another of those compilers that tenatiously guards their stupidity.  Reinterpreting a negative number as an unsigned value results in a very large number on two's complement machines.  Are there any modern machines that don't use two's complement?

Using CURLOPT_LASTENTRY should also work as a last resort since it has the down side of library updates adding new enum values and changing the last entry value.


- rmudgett


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On March 31, 2015, 8:59 p.m., Diederik de Groot wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/4533/
> -----------------------------------------------------------
> 
> (Updated March 31, 2015, 8:59 p.m.)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Bugs: ASTERISK-24917
>     https://issues.asterisk.org/jira/browse/ASTERISK-24917
> 
> 
> Repository: Asterisk
> 
> 
> Description
> -------
> 
> clang's static analyzer will throw quite a number warnings / errors during compilation, some of which can be very helpfull in finding corner-case bugs
> 
> clang compiler warning:-Wtautological-compare
> 
> Changes:
> /branches/13/channels/pjsip/dialplan_functions.c:869
> len is of type size_t, which is unsigned. It will not be able to hold a value < 0
> 
> /branches/13/funcs/func_curl.c:174
> Not a 100% sure how to do this correctly. But assiging a negative value is problematic. Extending the enum in curl/curl.h is not possible either. I opted to use the enum last entry (CURL_LAST) which is currently not used for any thing. Another option would be to use one of the OBSOLETE VALUES like 16. Neither way is very nice though.
> 
> /branches/13/include/asterisk/app.h:988
> Needed to convey the error state returned by res/res_stasis_recording.c:stasis_app_recording_if_exists_parse
> 
> /branches/13/include/asterisk/cel.h:77
> Added to convey not-found or error state. Not sure which name would be prefered for such an enum value.
> 
> /branches/13/main/cel.c:536
> Return actual enum instead of -1,l which can not be conveyed by this enum.
> 
> /branches/13/main/enum.c:260
> dn_expand return signed int
> 
> /branches/13/main/event.c:202
> enum type cannot be < 0
> 
> /branches/13/main/indications.c:362
> tone_data.freq1 and freq2 are unsigned int's so no need to check if < 0. Not sure what should happend when freq1 / freq2 are 0 already... (needs recheck by source owner)
> 
> /branches/13/main/presencestate.c:293
> Should use the actual enum value for INVALID State
> 
> /branches/13/main/security_events.c:432/890/1176/
> enum event_type cannot be <0
> 
> /branches/13/main/udptl.c:365/649/661
> encode_length returns and unsigned int, so checking if < 0 does not make sence. Not 100% if encode_length has side effects, so left the actual call the this function in place. (Needs to be rechecked by code-owner)
> 
> /branches/13/res/res_pjsip_exten_state.c:411
> Used a temporary int variable to be able to check the return value from ast_hint_presence_state.. Not very nice, but did not want to change the signature of this function.
> 
> /branches/13/res/res_stasis_playback.c:634
> operation is enum and cannot be < 0
> 
> /branches/13/res/res_stasis_recording.c:598/604
> recording->state / operation is enum and cannot be < 0
> 
> /branches/13/res/res_security_log.c:992
> enum event_type cannot be <0
> 
> use of ARRAY_IN_BOUNDS with enum results in tautological comparison for the lower limit which is always true.
> 
> 
> Diffs
> -----
> 
>   /branches/13/res/res_stasis_recording.c 433444 
>   /branches/13/res/res_stasis_playback.c 433444 
>   /branches/13/res/res_pjsip_exten_state.c 433444 
>   /branches/13/res/ari/resource_channels.c 433444 
>   /branches/13/res/ari/resource_bridges.c 433444 
>   /branches/13/main/udptl.c 433444 
>   /branches/13/main/security_events.c 433444 
>   /branches/13/main/presencestate.c 433444 
>   /branches/13/main/indications.c 433444 
>   /branches/13/main/event.c 433444 
>   /branches/13/main/enum.c 433444 
>   /branches/13/main/cel.c 433444 
>   /branches/13/main/app.c 433444 
>   /branches/13/include/asterisk/utils.h 433444 
>   /branches/13/include/asterisk/logger.h 433444 
>   /branches/13/include/asterisk/cel.h 433444 
>   /branches/13/include/asterisk/app.h 433444 
>   /branches/13/funcs/func_curl.c 433444 
>   /branches/13/channels/pjsip/dialplan_functions.c 433444 
>   /branches/13/channels/chan_skinny.c 433444 
> 
> Diff: https://reviewboard.asterisk.org/r/4533/diff/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> Diederik de Groot
> 
>

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