Question on fix for this error with --enable=all

[Michael Setzer II]

Program has 4 qsort options that give this.
fixzzallbz.cpp:557:42: style: C-style pointer casting [cstyleCast]
qsort(datax, num2, sizeof(datax[0]), (int ()(const void , const void *))strcmp);

Usually find it gives a do you mean option..
Have never had a problem, but if there is a more correct way to do it, would like to update it.
Thanks

[CHR]

A few ideas:

• use std::sort with a lambda
• write a wrapper function and use static_cast on the arguments
• use reinterpret_cast on strcmp

[Michael Setzer II]

Not clear on first one, since what I've found seems sort is for numbers?
Found something with second one.
Create
int cmpstr(void const a, void const b)
{
char const aa = (char const )a;
char const bb = (char const )b;
return strcmp(aa, bb);
}
and change strcmp option to just cmpstr, but it then gives this output.
style: C-style pointer casting [cstyleCast]
char const aa = (char const )a;
^
style: C-style pointer casting [cstyleCast]
char const bb = (char const )b;
^
So, changes style issue on each qsort to just the two lines in cmpstr.

The cppcheck without --enable=all doesn't show anything, but with --enable=all it does.
The program seems to run fine with the original or with the cmpstr mode.

Just wondering if there is a more correct method to do this .

Thanks for the info. Will have to continue looking.

[CHR]

Using the -v option, the output is

bar.cpp:2:18: style: C-style pointer casting detected. C++ offers four different kinds of casts as replacements: static_cast, const_cast, dynamic_cast and reinterpret_cast. A C-style cast could evaluate to any of those automatically, thus it is considered safer if the programmer explicitly states which kind of cast is expected. See also: https://www.securecoding.cert.org/confluence/display/cplusplus/EXP05-CPP.+Do+not+use+C-style+casts. [cstyleCast]
  return strcmp((const char*)a, (const char*)b);
                 ^

That's why I wrote "use static_cast on the arguments".
Btw, std::sort is a generic sorting algorithm.

[Michael Setzer II]

I must be missing something. I've look at a number of links that say they work, but compiler gives a bunch of error lines?? The old style shell sort works perfectly?

Tried a number of things with various different cmp setups, but none compiled.
Have fedora 37 with latest compiler.
real programs have arrays of 300 to 700 strings, but did a simple example.

#include <cstdio></cstdio>

include <cstdlib></cstdlib>

include <cstring></cstring>

include <algorithm></algorithm>

using namespace std;
bool cmp(const char str1, const char str2){
if(strcmp(str1, str2)<0) return true;
else return false;
}
int main()
{
char temp[20], test[10][20]={ "Xray", "Milk", "Apple", "Orange", "Cat", "Dog", "Tree", "Motorcycle", "Tishawnna"};
int i,j;
for(i=0;i<10;i++) printf("%s\n",test[i]);
// sort(test,test+8,cmp);
// std::sort(std::begin(test), std::end(test));
// std::sort(test, test+8, { return strcmp(lhs,rhs) < 0; });
for(i=0;i<9;i++)
for(j=i+1;j<=9;j++)
if(strcmp(test[i],test[j])>0) { strcpy(temp,test[i]); strcpy(test[i],test[j]); strcpy(test[j],temp); };
for(i=0;i<10;i++) printf("%s\n",test[i]);
return 0;
}

[Michael Setzer II]

Tried some things, and found a solution, but is strange.
sort2 version has cppcheck --enable all report the earlier style message.
sort3 and sort4 don't give error, but strangely all three compiles produce identical binary files after strip??
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;
int cmpstr(void const a, void const b)
{
// from sort2.cpp
// char const aa = (char const )a;
// char const bb = (char const )b;
// return strcmp(aa, bb);
// from sort3.cpp
// char const aa = static_cast<char const="" *="">(a);
// char const </char>bb = static_cast<char const="" *="">(b);
// return strcmp( aa, bb);
// from sort4.cpp
return strcmp( static_cast<char const="" *="">(a), static_cast<char const="" *="">(b));
}</char></char></char></cstring></cstdlib></cstdio>

int main()
{
char test[10][20]={ "Xray", "Milk", "Apple", "Orange", "Cat", "Dog", "Tree", "Motorcycle", "Tishawnna"};
int i;
for(i=0;i<10;i++) printf("%s\n",test[i]);
qsort(test, 9, sizeof(test[0]), cmpstr);
for(i=0;i<10;i++) printf("%s\n",test[i]);
return 0;
}

So, static_cast gets rid of style error, but binary code is same??

[CHR]

This is expected, since the semantics of the program remain the same (it is a style warning after all).
std::sort must be able to assign the elements that it sorts.
Example: https://godbolt.org/z/c8hsf3jjE

[Michael Setzer II]

Thanks for al the info. Search had mentioned something about there error might cause run time error that the compiler wouldn't catch with the Cstyle casting? That's why I was looking for solution. Seems the sort would require complete redo of the C style arrays that are created elsewhere in program. Example seems to require more than what is needed with qsort or the simple old shell sort.
Interesting info. thanks again.