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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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This non-compliant code example, however, does comply with ERR30-C. Set errno to zero before calling a function, and use it only after the function returns a value indicating failure.
Compliant Solution
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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|---|---|---|
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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;
int rc;
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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