[PATCH] assert: Support assert as variadic macro for C++26 [PR27276]

[Tomasz Kaminski]

On Thu, Feb 5, 2026 at 4:40 PM Tomasz Kaminski <tkaminsk@redhat.com> wrote:

>
>
> On Thu, Feb 5, 2026 at 4:36 PM Florian Weimer <fweimer@redhat.com> wrote:
>
>> * Tomasz Kamiński:
>>
>> > +#  if __ASSERT_VARIADIC
>> > +#    define assert(...)
>>       \
>> > +     ((__VA_ARGS__)                                                  \
>> > +      ? (void)(1 ? 1 : bool(__VA_ARGS__))                            \
>> > +      : __assert_fail (#__VA_ARGS__, __ASSERT_FILE, __ASSERT_LINE,   \
>> > +                       __ASSERT_FUNCTION))
>>
>> Doesn't this evaluate __VA_ARGS__ multiple times?
>>
> I got the same question initially when I saw this solution, but
> the second bool(__VA_ARGS) is in the false branch of the ternary:
> 1 ? 1 : bool(__VA_ARGS__)
> So it is never evaluated.
>
I will add following in do_test in test-assert-c++.cc, as there seem to be
no
check for lack of double evaluation:

diff --git a/assert/tst-assert-c++.cc b/assert/tst-assert-c++.cc
index 7fb8bbfe26..534a191fbd 100644
--- a/assert/tst-assert-c++.cc
+++ b/assert/tst-assert-c++.cc
@@ -90,6 +90,13 @@ do_test ()
     // assert(E::e1);
   }

+  {
+    int i = 0;
+    assert(++i);
+    if (i != 1)
+      return 1;
+  }
+
   return 0;
 }
 #define NDEBU

>
>
>>
>> Thanks,
>> Florian
>>
>>
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