Make array & new_array const-correct in test_is_string_in_array.

[sp1ff]

When building on Arch, I saw a few compilation errors of the form:

string_lib_test.c:873:40: error: passing argument 2 of ‘IsStringInArray’ from incompatible pointer type [-Wincompatible-pointer-types]

This small commit fixes them.

[mender-test-bot]

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[olehermanse]

Thanks!

[larsewi]

Thanks 🚀

One note:
Since the new_array variable is allocated on the heap and later free'd, it may be better to keep it char ** and instead explicitly cast it to const char ** when passing it as an argument to IsStringInArray. The reason is that free(3) takes a void * as an argument (not const void *).

[olehermanse]

Thanks 🚀

One note: Since the new_array variable is allocated on the heap and later free'd, it may be better to keep it char ** and instead explicitly cast it to const char ** when passing it as an argument to IsStringInArray. The reason is that free(3) takes a void * as an argument (not const void *).

No, how he did it is correct. This is a double pointer, strings is a non-const pointer, to a non-const pointer, to a const char in memory.

#include <stdio.h> // printf()                                                                                                                               
#include <stdlib.h> // calloc()                                                                                                                              

int main(void)
{
  const char **strings = calloc(3, sizeof(const char *));

  // C compiler is not very strict with string literals                                                                                                      
  strings[0] = "hello";	// This works regardless of whether strings has const or not                                                                         

  // After assigning to a typed variable, the compiler will be more strict:                                                                                    
  const char *world = "world";
  strings[1] = world; // Const correctness is checked here.                                                                                                  
  printf("%s, %s\n", strings[0], strings[1]);

  void *temp = strings;
  // const void *temp = strings; // This would not work, const mismatch.                                                                                     

  free(temp); // free(strings) would also work                                                                                                               
  return 0;
}

$ gcc -Wall -Werror -Wpedantic test.c -o test && ./test
hello, world

Wrong

[sp1ff]

Thanks-- works much better!