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error: preserve errno when saving last error

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It is common to see the sequence:

virErrorPtr save_err = virSaveLastError();
// do cleanup
virSetError(save_err);
virFreeError(save_err);

on cleanup paths.  But for functions where it is desirable to
return the errno that caused failure, this sequence can clobber
that errno.  virFreeError was already safe; this makes the other
two functions in the sequence safe as well, assuming all goes
well (on OOM, errno will be clobbered, but then again, save_err
won't reflect the real error that happened, so you are no longer
preserving the real situation - that's life with OOM).

* src/util/virterror.c (virSaveLastError, virSetError): Preserve
errno.
This commit is contained in:
Eric Blake 2011-07-20 17:07:59 -06:00
parent 1468359f16
commit 979b784be2
1 changed files with 13 additions and 4 deletions
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17
src/util/virterror.c
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@ -295,18 +295,24 @@ virGetLastError(void)
* Can be used to re-set an old error, which may have been squashed by * Can be used to re-set an old error, which may have been squashed by
* other functions (like cleanup routines). * other functions (like cleanup routines).
* *
* Returns 0 on success, 1 on failure * Returns 0 on success, -1 on failure. Leaves errno unchanged.
*/ */
int int
virSetError(virErrorPtr newerr) virSetError(virErrorPtr newerr)
{ {
virErrorPtr err; virErrorPtr err;
int saved_errno = errno;
int ret = -1;
err = virLastErrorObject(); err = virLastErrorObject();
if (!err) if (!err)
return -1; goto cleanup;
virResetError(err); virResetError(err);
return virCopyError(newerr, err); ret = virCopyError(newerr, err);
cleanup:
errno = saved_errno;
return ret;
} }
/** /**
@ -339,7 +345,8 @@ virCopyLastError(virErrorPtr to)
/** /**
* virSaveLastError: * virSaveLastError:
* *
* Save the last error into a new error object. * Save the last error into a new error object. On success, errno is
* unchanged; on failure, errno is ENOMEM.
* *
* Returns a pointer to the copied error or NULL if allocation failed. * Returns a pointer to the copied error or NULL if allocation failed.
* It is the caller's responsibility to free the error with * It is the caller's responsibility to free the error with
@ -349,11 +356,13 @@ virErrorPtr
virSaveLastError(void) virSaveLastError(void)
{ {
virErrorPtr to; virErrorPtr to;
int saved_errno = errno;
if (VIR_ALLOC(to) < 0) if (VIR_ALLOC(to) < 0)
return NULL; return NULL;
virCopyLastError(to); virCopyLastError(to);
errno = saved_errno;
return to; return to;
} }