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| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <errno.h>
#include <stdio.h>
#include <string.h>
void f(FILE *fp) {
fpos_t pos;
errno = 0;
if (0 != fgetpos(fp, &pos) {
char *errmsg = strerror(errno);
printf("Could not get the file position because of %s\n",
errmsg);
}
} |
Note that this code first sets errno to 0 to comply with ERR30-C. Set errno to zero before calling a library function known to set errno, and check errno only after the function returns a value indicating failure.
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| Code Block | ||||
|---|---|---|---|---|
| ||||
#define __STDC_WANT_LIB_EXT1__ 1
#include <errno.h>
#include <stdio.h>
#include <string.h>
void f(FILE *fp) {
fpos_t pos;
errno = 0;
if (0 != fgetpos(fp, &pos) {
char errmsg[BUFSIZ64];
if (strerror_s(errmsg, BUFSIZsizeof(errmsg), errno) != 0) {
/* Handle error */
}
printf("Could not get the file position because of %s\n",
errmsg);
}
} |
Note that because of the optional nature of Annex K, strerror_s() may not be available in all implementations.
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| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <errno.h>
#include <stdio.h>
#include <string.h>
void f(FILE *fp) {
fpos_t pos;
errno = 0;
if (0 != fgetpos(fp, &pos) {
char errmsg[BUFSIZ64];
if (strerror_r(errno, errmsg, BUFSIZsizeof(errmsg)) != 0) {
/* Handle error */
}
printf("Could not get the file position because of %s\n",
errmsg);
}
} |
Note that Linux provides two versions of strerror_r(), known as the XSI-compliant version and the GNU-specific version. This compliant solution assumes the XSI-compliant version. You can get the XSI-compliant version if you compile applications in the way POSIX requires (that is, by defining _POSIX_C_SOURCE or _XOPEN_SOURCE appropriately). Check your strerror_r() manual page to see which version(s) are available on your system.
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Tool | Version | Checker | Description |
|---|---|---|---|
Compass/ROSE |
|
| A module written in Compass/ROSE can detect violations of this rule |
Related Guidelines
...
| [Historical information about POSIX.1 Thread Safety] | Section 2.9.1 |
| [ISO/IEC 9899:2011] | Section 7.24.6.2, "The |
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