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What is the safest way to pass strings in C?

I have a program in C using Solaris with VERY ancient compatibility. Many examples, even here on SO, do not work, as well as a lot of code written on Mac OS X.

So, when using very strict C, what is the safest way to pass strings?

I am currently using char pointers everywhere, because of what I thought was simplicity. So I have functions that return char *, I pass them char *, etc.

I already see strange behavior, for example, like char *, when I entered the function, and then the value mysteriously disappeared or was damaged / overwritten after something simple, for example, one printf () or malloc to another pointer.

One approach to functions, which I'm sure is wrong, could be:

char *myfunction(char *somestr) {    
  char localstr[MAX_STRLENGTH] = strcpy(localstr, somestr);
  free(somestr);
  /* ... some work ... */
  char *returnstr = strdup(localstr);
  return returnstr;
}

... . - ?

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char *get_fullpath(char *command, char *paths) {
  printf("paths inside function %s\n", paths); // Prints value of paths just fine

  char *fullpath = malloc(MAX_STRLENGTH*sizeof(char*));

  printf("paths after malloc %s\n", paths); // paths is all of a sudden just blank
}
+5
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2
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+12

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char localstr[MAX_STRLENGTH] = strcpy(localstr, somestr);

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char localstr[MAX_STRLENGTH];
strcpy(localstr, somestr);

, free() . free() , malloc(). , .

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// use a prototype like this to use the same buffer for both input and output
int modifyMyString(char buffer[], int bufferSize) {
    // .. operate you find in buffer[],
    //    leaving the result in buffer[]
    //    and be sure not to exceed buffer length
    // depending how it went, return EXIT_FAILURE or maybe
    return EXIT_SUCCESS;

// or separate input and outputs
int workOnString(char inBuffer[], int inBufSize, char outBuffer[], int outBufSize) {
    // (notice, you could replace inBuffer with const char *)
    // leave result int outBuffer[], return pass fail status
    return EXIT_SUCCESS;

malloc() free() .

+4

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if (strcmp(getMeSomeString(),stringIWantToCompareItTo)==0) etc

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char* someString=getMeSomeString();
int f=strcmp(someString,stringIWantToCompareItTo);
free(someString);
if (f==0)
etc

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