| Message ID | 20201113011340.463563-6-eblake@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | Common macros for QAPI list growth | expand |
Eric Blake <eblake@redhat.com> writes: > Similar to the existing QAPI_LIST_PREPEND, but designed for use where > we want to preserve insertion order. Callers will be added in > upcoming patches. Note the difference in signature: PREPEND takes > List*, APPEND takes List**. > > Signed-off-by: Eric Blake <eblake@redhat.com> > --- > include/qapi/util.h | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/include/qapi/util.h b/include/qapi/util.h > index 6178e98e97a5..8b4967990c0d 100644 > --- a/include/qapi/util.h > +++ b/include/qapi/util.h > @@ -37,4 +37,17 @@ int parse_qapi_name(const char *name, bool complete); > (list) = _tmp; \ > } while (0) > > +/* > + * For any pointer to a GenericList @tail, insert @element at the back and > + * update the tail. > + * > + * Note that this macro evaluates @element exactly once, so it is safe > + * to have side-effects with that argument. > + */ > +#define QAPI_LIST_APPEND(tail, element) do { \ > + *(tail) = g_malloc0(sizeof(**(tail))); \ > + (*(tail))->value = (element); \ > + (tail) = &(*tail)->next; \ > +} while (0) > + > #endif Reviewed-by: Markus Armbruster <armbru@redhat.com>
On 11/17/20 6:51 AM, Markus Armbruster wrote: > Eric Blake <eblake@redhat.com> writes: > >> Similar to the existing QAPI_LIST_PREPEND, but designed for use where >> we want to preserve insertion order. Callers will be added in >> upcoming patches. Note the difference in signature: PREPEND takes >> List*, APPEND takes List**. >> >> Signed-off-by: Eric Blake <eblake@redhat.com> >> +#define QAPI_LIST_APPEND(tail, element) do { \ >> + *(tail) = g_malloc0(sizeof(**(tail))); \ >> + (*(tail))->value = (element); \ >> + (tail) = &(*tail)->next; \ Hmm; I'm inconsistent on whether to spell things '*tail' or '*(tail)'. I don't think any of the callers converted in patches 6 or 7 care about the difference, but for maximal copy-paste portability, the use of the macro parameter should be surrounded by () anywhere that could otherwise cause a mis-parse on some arbitrary expression with an operator at higher precedence than unary * (hmm, the only such operators are all suffix operators; so maybe the *(tail) is overkill...) > > Reviewed-by: Markus Armbruster <armbru@redhat.com> >
Eric Blake <eblake@redhat.com> writes: > On 11/17/20 6:51 AM, Markus Armbruster wrote: >> Eric Blake <eblake@redhat.com> writes: >> >>> Similar to the existing QAPI_LIST_PREPEND, but designed for use where >>> we want to preserve insertion order. Callers will be added in >>> upcoming patches. Note the difference in signature: PREPEND takes >>> List*, APPEND takes List**. >>> >>> Signed-off-by: Eric Blake <eblake@redhat.com> > >>> +#define QAPI_LIST_APPEND(tail, element) do { \ >>> + *(tail) = g_malloc0(sizeof(**(tail))); \ >>> + (*(tail))->value = (element); \ >>> + (tail) = &(*tail)->next; \ > > Hmm; I'm inconsistent on whether to spell things '*tail' or '*(tail)'. > I don't think any of the callers converted in patches 6 or 7 care about > the difference, but for maximal copy-paste portability, the use of the > macro parameter should be surrounded by () anywhere that could otherwise > cause a mis-parse on some arbitrary expression with an operator at > higher precedence than unary * (hmm, the only such operators are all > suffix operators; so maybe the *(tail) is overkill...) Good habit: enclose macro parameter in parenthesis unless there is a reason not to. Let's do it here, too. >> Reviewed-by: Markus Armbruster <armbru@redhat.com>
diff --git a/include/qapi/util.h b/include/qapi/util.h index 6178e98e97a5..8b4967990c0d 100644 --- a/include/qapi/util.h +++ b/include/qapi/util.h @@ -37,4 +37,17 @@ int parse_qapi_name(const char *name, bool complete); (list) = _tmp; \ } while (0) +/* + * For any pointer to a GenericList @tail, insert @element at the back and + * update the tail. + * + * Note that this macro evaluates @element exactly once, so it is safe + * to have side-effects with that argument. + */ +#define QAPI_LIST_APPEND(tail, element) do { \ + *(tail) = g_malloc0(sizeof(**(tail))); \ + (*(tail))->value = (element); \ + (tail) = &(*tail)->next; \ +} while (0) + #endif
Similar to the existing QAPI_LIST_PREPEND, but designed for use where we want to preserve insertion order. Callers will be added in upcoming patches. Note the difference in signature: PREPEND takes List*, APPEND takes List**. Signed-off-by: Eric Blake <eblake@redhat.com> --- include/qapi/util.h | 13 +++++++++++++ 1 file changed, 13 insertions(+)