[libvirt] [PATCHv3] command: improve behavior on no output
Matthias Bolte
matthias.bolte at googlemail.com
Tue Dec 7 22:17:43 UTC 2010
2010/12/7 Eric Blake <eblake at redhat.com>:
> Guarantee that outbuf/errbuf are allocated on success, even if to the
> empty string. Caller always has to free the result, and empty output
> check requires checking if *outbuf=='\0'. Makes the API easier to use
> safely. Failure is best effort allocation (some paths, like
> out-of-memory, cannot allocate a buffer, but most do), so caller must
> free buffer on failure; but this now guarantees that VIR_FREE(buf)
> will be safe.
>
> * docs/internals/command.html.in: Update documentation.
> * src/util/command.c (virCommandSetOutputBuffer)
> (virCommandSetErrorBuffer, virCommandProcessIO) Guarantee empty
> string on no output.
> * tests/commandtest.c (test17): New test.
> ---
>
> Everyone liked the safety of v2 over the speed of v1; and in looking
> at it more, I found even more ways to make it safer. Hence this v3.
>
> docs/internals/command.html.in | 12 ++++++--
> src/util/command.c | 53 ++++++++++++++++++++++++++++--------
> tests/commandtest.c | 58 ++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 108 insertions(+), 15 deletions(-)
> diff --git a/tests/commandtest.c b/tests/commandtest.c
> index b7261e9..20e56bc 100644
> --- a/tests/commandtest.c
> +++ b/tests/commandtest.c
> @@ -595,6 +595,63 @@ cleanup:
> return ret;
> }
>
> +/*
> + * Test string handling when no output is present.
> + */
> +static int test17(const void *unused ATTRIBUTE_UNUSED)
> +{
> + virCommandPtr cmd = virCommandNew("/bin/true");
> + int ret = -1;
> + char *outbuf;
> + char *errbuf;
> +
> + virCommandSetOutputBuffer(cmd, &outbuf);
> + if (outbuf != NULL) {
> + puts("buffer not sanitized at registration");
> + goto cleanup;
> + }
> +
> + if (virCommandRun(cmd, NULL) < 0) {
> + virErrorPtr err = virGetLastError();
> + printf("Cannot run child %s\n", err->message);
> + goto cleanup;
> + }
> +
> + if (!outbuf || *outbuf) {
> + puts("output string not allocated");
The error message doesn't fit to the *outbuf != \0 test.
> + goto cleanup;
> + }
> + VIR_FREE(outbuf);
> + if ((outbuf = strdup("should not be leaked")) == NULL) {
> + puts("test framework failure");
> + goto cleanup;
> + }
> +
> + virCommandSetErrorBuffer(cmd, &errbuf);
> + if (errbuf != NULL) {
> + puts("buffer not sanitized at registration");
> + goto cleanup;
> + }
> +
> + if (virCommandRun(cmd, NULL) < 0) {
> + virErrorPtr err = virGetLastError();
> + printf("Cannot run child %s\n", err->message);
> + goto cleanup;
> + }
> +
> + if (!outbuf || *outbuf || !errbuf || *errbuf) {
> + puts("output strings not allocated");
The error message doesn't fit to the *{out|err}buf != \0 test.
Also what about the case when running /bin/true prints to {std|err}out
for some reason? :)
ACK.
Matthias
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