Re: pthread.h is breaking programs that use strtok_r and rand_r

["John E. Bossom" <drifting@pioneerwireless.ca>]

1998!


Quoting Ross Johnson <Ross.Johnson@homemail.com.au>:

> They may have been much more useful back in 1996 however I've removed
> them from the current CVS trunk.
>
> rand_r was used in two tests.
>
> Thanks.
>
> On 29/12/2010 5:33 AM, Lubashev, Igor wrote:
>> Hi!
>>
>> First of all, thanks for a great project!
>>
>> I do have some issues to report, though.
>>
>> Header pthread.h is expected to be included by client code, but it   
>> is breaking client code that uses strtok_r and rand_r.  Yes, these   
>> macros are not defined on Windows, but people trying to write   
>> portable code will likely provide their definitions for these POSIX  
>>  functions.  Unfortunately, if pthread.h is included after the   
>> headers providing these definitions, pthread.h will break client   
>> code.  The definitions for these macros in pthread.h are not   
>> standard compliant.
>>
>> 1.  pthread.h's definition for strtok_r:
>>
>>    #define strtok_r( _s, _sep, _lasts )  ( *(_lasts) = strtok(   
>> (_s), (_sep) ) )
>>
>> It completely ignores _lasts field, which is not standard   
>> compliant.  Standard requires: "Different strings may be parsed   
>> concurrently using sequences of calls to strtok_r() that specify   
>> different saveptr arguments."
>>
>>
>> --- Test program on Windows:
>>
>> #include<stdio.h>
>> #include<stdlib.h>
>> #include<string.h>
>>
>> #define strtok_r strtok_s
>>
>> /* #include<pthread.h>  */
>>
>> int main(void)
>> {
>>   char str1[] = "A day";
>>   char str2[] = "A night";
>>   char *save1, *save2;
>>   strtok_r(str1, "  ",&save1);
>>   strtok_r(str2, "  ",&save2);
>>   printf("%s and %s\n", strtok_r(NULL, "  ",&save1), strtok_r(NULL,  
>>  " ",&save2));
>>   return EXIT_SUCCESS;
>> }
>>
>>
>> The result is expected:  "day and night"
>>
>> However, if I uncomment #include<pthread.h>, the result is: "(null)  
>>  and night".
>>
>> --- Note:
>>
>> Windows already has a compatible function called strtok_s.
>>
>> #define strtok_r strtok_s
>>
>>
>>
>> 2.  pthread.h's definition for rand_r:
>>
>>   #define rand_r( _seed ) ( _seed == _seed ? rand() : rand() )
>>
>> It completely ignores the _seed.  The standard requires rand_r to   
>> use its seed as its state.  User code can rely on a deterministic   
>> initial seed to receive a deterministic sequence of pseudo-random   
>> numbers.  This is very useful in debugging, for example.  Moreover,  
>>  rand_r output is not supposed to affect or be affected by calls to  
>>  rand or rand_r with a different seed address.
>>
>>
>>
>> In general, it is a very bad form for pthread.h to define and drop   
>> into client's global scope macros that are not related to pthreads   
>> and are likely to collide on names with client's own macros or   
>> functions.
>>
>> I hope the next release of pthread-win32 will address these issues.
>>
>>
>> Cheers,
>>
>> - Igor Lubashev