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This noncompliant code example shows a function called opener() that returns errno error codes. However, the function is declared as returning an int. Consequently, the meaning of the return value is not as clear as it could be.
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enum { NO_FILE_POS_VALUES = 3 };
int opener(
FILE *file,
int *width,
int *height,
int *data_offset
) {
int file_w;
int file_h;
int file_o;
fpos_t offset;
if (file == NULL) { return EINVAL; }
errno = 0;
if (fgetpos(file, &offset) != 0) { return errno; }
if (fscanf(file, "%i %i %i", &file_w, &file_h, &file_o)
!= NO_FILE_POS_VALUES) {
return EIO;
}
errno = 0;
if (fsetpos(file, &offset) != 0) { return errno; }
if (width != NULL) { *width = file_w; }
if (height != NULL) { *height = file_h; }
if (data_offset != NULL) { *data_offset = file_o; }
return 0;
}
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In this compliant solution, the opener() function returns a value of type errno_t, providing a clear indication that this function returns an error code.
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#include <errno.h>
enum { NO_FILE_POS_VALUES = 3 };
errno_t opener(
FILE *file,
int *width,
int *height,
int *data_offset
) {
int file_w;
int file_h;
int file_o;
fpos_t offset;
if (file == NULL) { return EINVAL; }
errno = 0;
if (fgetpos(file, &offset) != 0 ) { return errno; }
if (fscanf(file, "%i %i %i", &file_w, &file_h, &file_o)
!= NO_FILE_POS_VALUES) {
return EIO;
}
errno = 0;
if (fsetpos(file, &offset) != 0 ) { return errno; }
if (width != NULL) { *width = file_w; }
if (height != NULL) { *height = file_h; }
if (data_offset != NULL) { *data_offset = file_o; }
return 0;
}
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