[libvirt] [PATCH] error: preserve errno when saving last error
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.
---
Fixes an errno-clobbering situation pointed out here:
https://www.redhat.com/archives/libvir-list/2011-July/msg01382.html
src/util/virterror.c | 17 +++++++++++++----
1 files changed, 13 insertions(+), 4 deletions(-)
diff --git a/src/util/virterror.c b/src/util/virterror.c
index 0c7698a..07f8b45 100644
--- a/src/util/virterror.c
+++ b/src/util/virterror.c
@@ -295,18 +295,24 @@ virGetLastError(void)
* Can be used to re-set an old error, which may have been squashed by
* other functions (like cleanup routines).
*
- * Returns 0 on success, 1 on failure
+ * Returns 0 on success, -1 on failure. Leaves errno unchanged.
*/
int
virSetError(virErrorPtr newerr)
{
virErrorPtr err;
+ int saved_errno = errno;
+ int ret = -1;
+
err = virLastErrorObject();
if (!err)
- return -1;
+ goto cleanup;
virResetError(err);
- return virCopyError(newerr, err);
+ ret = virCopyError(newerr, err);
+cleanup:
+ errno = saved_errno;
+ return ret;
}
/**
@@ -339,7 +345,8 @@ virCopyLastError(virErrorPtr to)
/**
* 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.
* It is the caller's responsibility to free the error with
@@ -349,11 +356,13 @@ virErrorPtr
virSaveLastError(void)
{
virErrorPtr to;
+ int saved_errno = errno;
if (VIR_ALLOC(to) < 0)
return NULL;
virCopyLastError(to);
+ errno = saved_errno;
return to;
}
--
1.7.4.4