On Mon, Jan 21, 2019 at 03:13:21PM +0000, Richard W.M. Jones wrote:
> GCC 9 gives pages of errors like:
>
> qemumonitorjsontest.c: In function 'mymain':
> qemumonitorjsontest.c:2904:9: error: jump skips variable initialization [-Werror=jump-misses-init]
> 2904 | goto cleanup;
> | ^~~~
> qemumonitorjsontest.c:3111:2: note: label 'cleanup' defined here
> 3111 | cleanup:
> | ^~~~~~~
> qemumonitorjsontest.c:2920:54: note: '({anonymous})' declared here
> 2920 | simpleFunc = (testQemuMonitorJSONSimpleFuncData) {.xmlopt = driver.xmlopt, \
> | ^
> qemumonitorjsontest.c:3008:5: note: in expansion of macro 'DO_TEST_GEN'
> 3008 | DO_TEST_GEN(qemuMonitorJSONBlockdevMediumInsert);
> | ^~~~~~~~~~~
Ok, it is complaining about "simpleFunc", because for the 5 locally
declared variables, we've done explicit initialization before any
goto's are encountered. The fun thing is that the cleanup: block
does not reference "simpleFunc" in any way - it is only ever used
immediately after it is initialized.
So GCC is warning about something that can't happen here.
The definition of -Wjump-misses-init says
[quote]
Warn if a 'goto' statement or a 'switch' statement jumps forward
across the initialization of a variable, or jumps backward to a
label after the variable has been initialized. This only warns
about variables that are initialized when they are declared.
[/quote]
we're jumping forwards here, but the last sentance suggests it would
only warn if you are jumping over the variable declaration. ie if we
had
testQemuMonitorJSONSimpleFuncData simpleFunc;
in the middle of the method, instead of top of the method. So either
they've intentionally expanded the scope of the warning, or this is
a bug in GCC.
Either way the simple solution is probably just:
testQemuMonitorJSONSimpleFuncData simpleFunc = NULL;
>
> By moving the cleanup section up near the top of the function we can
> avoid this. I think a better way might be to disable the warning.
> ---
> tests/qemumonitorjsontest.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/tests/qemumonitorjsontest.c b/tests/qemumonitorjsontest.c
> index 1a8a31717f..299c5f0cbe 100644
> --- a/tests/qemumonitorjsontest.c
> +++ b/tests/qemumonitorjsontest.c
> @@ -2900,8 +2900,12 @@ mymain(void)
>
> if (!(qapiData.schema = testQEMUSchemaLoad())) {
> VIR_TEST_VERBOSE("failed to load qapi schema\n");
> - ret = -1;
> - goto cleanup;
> + cleanup:
> + VIR_FREE(metaschemastr);
> + virJSONValueFree(metaschema);
> + virHashFree(qapiData.schema);
> + qemuTestDriverFree(&driver);
> + return -1;
> }
>
> #define DO_TEST(name) \
> @@ -3098,7 +3102,6 @@ mymain(void)
> if (!(metaschema = testQEMUSchemaGetLatest()) ||
> !(metaschemastr = virJSONValueToString(metaschema, false))) {
> VIR_TEST_VERBOSE("failed to load latest qapi schema\n");
> - ret = -1;
> goto cleanup;
> }
>
> @@ -3108,7 +3111,6 @@ mymain(void)
>
> #undef DO_TEST_QAPI_SCHEMA
>
> - cleanup:
> VIR_FREE(metaschemastr);
> virJSONValueFree(metaschema);
> virHashFree(qapiData.schema);
> --
> 2.20.1
>
> --
> libvir-list mailing list
> libvir-list@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/libvir-list
Regards,
Daniel
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