Re: [Valgrind-users] seemingly bogus error reports

[David C. <dcc...@ac...>]

On 9/14/2019 12:11 PM, Fred Smith wrote:
>
> Hi all!
>
> I’m new to this list, but have used Valgrind many times in the past.
>
> Today I’m making a serious effort to clean up a non-trivial body of 
> code, and have run into a number of error reports like this one:
>
> ==00:00:00:11.329 1533== Conditional jump or move depends on 
> uninitialised value(s)
>
> ==00:00:00:11.329 1533==    at 0x7B0BCC2: ttci2n (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x7B20DF5: ttcacs (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x7AF2503: ttcdrv (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x7AE14C8: nioqwa (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x7AC35CB: upirtrc (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x7ACDDE5: kpurcsc (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x7AC710D: kpuexec (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x7AC3F78: OCIStmtExecute (in 
> /home/interface/interface/oralib-12/lib/libclntsh.so.12.1)
>
> ==00:00:00:11.329 1533==    by 0x45078D: HS_do_OCI_stuff (HS_oci.c:1460)
>
> ==00:00:00:11.329 1533==    by 0x407DA0: HS_send2HS (HS_thr_out.c:261)
>
> ==00:00:00:11.329 1533==    by 0x4083BB: HS_convertandsend 
> (HS_thr_out.c:468)
>
> ==00:00:00:11.329 1533==    by 0x40884E: HS_out_msg (HS_thr_out.c:629)
>
> ==00:00:00:11.329 1533==    by 0x40913C: HS_out_main (HS_thr_out.c:933)
>
> ==00:00:00:11.329 1533==    by 0x409797: HS_main_out (HS_thr_out.c:1172)
>
> ==00:00:00:11.329 1533==    by 0x9C50DD4: start_thread 
> (pthread_create.c:307)
>
> ==00:00:00:11.329 1533==  Uninitialised value was created by a stack 
> allocation
>
> ==00:00:00:11.329 1533==    at 0x407C67: HS_send2HS (HS_thr_out.c:231)
>
> ==00:00:00:11.329 1533==
>
> The problem with that report is that line 231 contains no explicit code:
>
> static HS_IF_STATE HS_send2HS (HS_out_thread * myoutthr,
>
>                                 HS_MSGBUF * msgbuf,
>
>                                 HS_IF_PARMS * ifparms,
>
>                                 xmlChar * xmlbufptr,
>
>                                 char * HS_resp,
>
>                                 HS_patdat * patdat,
>
>                                 char * databuf)
>
> { ç line 231
>
>                 HS_IF_STATE status = OK;
>
>                 int success, warnings;
>
>                 int numtries = 0
>
> I can’t find anything that’s allocated in that function that would be 
> un-initialized later in the program, and I don’t know what it thinks 
> is on line 231.
>
> Advice will be appreciated, thanks in advance!
>

The allocation is probably in the function's stack frame, which would be 
set up at function entry.  The compiler probably assigned line 231 to 
that task.  I see line 261 in your call stack; what local variables does 
it use?

-- 
     David Chapman      dcc...@ac...
     Chapman Consulting -- San Jose, CA
     EDA Software Developer, Expert Witness
     www.chapman-consulting-sj.com
     2018-2019 Chair, IEEE Consultants' Network of Silicon Valley