qsort and bsearch warning at compilation... 1

[fl0ra]

#define L_VARIABLE 0xFF
#define N_VARIABLE 173

char sDS_PKG_VariableName[N_VARIABLE][L_VARIABLE]={"ANT_PC_GPS","AS2DEG","BOLTZ","CHANNEL_ID","CLK_ERR_GPS_SAT","CLOCK_BIAS","COARSE_OBT0","COARSE_UTC0","COR_SPAC","CPM_CORR_L1","CPM_CORR_L2","CPM_L1","CPM_L2","C_A_PRM_CORR_SM","C_A_PRM_L1","C_L","C_PN","ClockOffset","ClockTimetag","DATA_THRES",/* 173 variables name I'm obviously not pasting them all... */
}

qsort(sDS_PKG_VariableName,N_VARIABLE,L_VARIABLE,strcmp);
if(bsearch("C_L",sDS_PKG_VariableName,N_VARIABLE,L_VARIABLE,strcmp)==NULL) {
/* blabla */
} else {
/* blabla */
}

ok nothing really special about it.
However when I compile with gcc it gives me those warnings:

warning: passing arg 4 of 'qsort' for incompatible pointer type
warning: passing arg 5 of 'bsearch' for incompatible pointer type


At the end of the day it works fine.
But I am wondering why do I get warnings like that because it is really "by-the-book" example of use qsort and bsearch.

Cheers

 

[ArkM]

Of course, qsort() signature is:

void qsort(void*, size_t, size_t, int (*)(const void*, const void*));

but strcmp() signature is:

int strcmp(const char*, const char*);

No any standard conversions between pointers to functions...
Well, in that case you may use brutal force (and controlled lie) method:

typedef int (*QScmpf)(const void*,const void*);
...
qsort(...,...,...,(QScmpf)strcmp);

It will be OK (in this case)...

 

[fl0ra]

LOL
ok I'll try that...
cheers.

 

[ArkM]

Some additions:
Strictly speaking (to conform with C Standard), in that cases we must write a minimal wrapper:

#ifdef __cplusplus
inline /* optional */
#endif
int StrCmp(const void* s1, const void* s2)
{
  return strcmp((const char*)s1,(const char*)s2);
}
...
qsort(....,StrCmp);

The (const char*) cast is optional in C, but we must do it in C++.
Apropos, use the same approach(es) for bsearch()...

 

[fl0ra]

yep. the first approach works great (obviously).
I'm gonna stick with that.

thank you very much indeed.