On Mon, Mar 16, 2020 at 10:35:05PM -0400, Tom Lane wrote:
> Michael Paquier <mich...@paquier.xyz> writes:
>> C++ does not allow defining a struct inside a sizeof() call, so in
>> this case StaticAssertExpr() does not work with the previous extension
>> in C++. StaticAssertStmt() does the work though.
>
> [ scratches head... ] A do{} is okay in an expression in C++ ??
cpp-fallback-fix.patch in [1] was doing that.
The fun does not stop here. gcc is fine when using that for C and
C++:
#define StaticAssertStmt(condition, errmessage) \
do { struct static_assert_struct { int static_assert_failure : (condition) ?
1 : -1; }; } while(0)
#define StaticAssertExpr(condition, errmessage) \
((void) ({ StaticAssertStmt(condition, errmessage); }))
But then problems come from MSVC which does not like the do{} part for
statements, and this works:
#define StaticAssertStmt(condition, errmessage) \
((void) sizeof(struct { int static_assert_failure : (condition) ? 1 : -1;
}))
#define StaticAssertExpr(condition, errmessage) \
StaticAssertStmt(condition, errmessage)
[1]: https://postgr.es/m/20200313115033.ga183...@paquier.xyz
--
Michael
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