Re: Make copyObject work in C++

Hi,

On 2026-01-20 20:07:15 +0100, Peter Eisentraut wrote:
> On 20.01.26 17:38, Andres Freund wrote:
> > > I have split your first patch further.  For a start, I left out the
> > > PG_MODULE_MAGIC*-related changes and disabled the module under MSVC. This
> > > has been committed.  I plan to let the buildfarm run with it for a day or
> > > two and then add in the basic MSVC support.
> > Seems like billbug doesn't like this:
> > 
> > https://buildfarm.postgresql.org/cgi-bin/show_log.pl?
> > nm=billbug&dt=2026-01-20%2016%3A00%3A02
> > 
> > gmake[1]: Entering directory
'/home/marcel/build-farm-20/buildroot/HEAD/pgsql.build/src/test/modules/test_cplusplusext'
> > g++ -Wall -Wpointer-arith -Wendif-labels -Wmissing-format-attribute -Wimplicit-fallthrough=3 -Wcast-function-type
-Wshadow=compatible-local-Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -g -O2 -fPIC
-fvisibility=hidden-fvisibility-inlines-hidden -I. -I. -I../../../../src/include -D_POSIX_C_SOURCE=200112L
-D__EXTENSIONS__-D_POSIX_PTHREAD_SEMANTICS  -I/usr/openssl/3/include -I/usr/include/libxml2     -c -o
test_cplusplusext.otest_cplusplusext.cpp
 
> > In file included from ../../../../src/include/postgres.h:48,
> >                   from test_cplusplusext.cpp:18:
> > ../../../../src/include/c.h:158:21: error: '_Noreturn' does not name a type; did you mean 'pg_noreturn'?
> >    158 | #define pg_noreturn _Noreturn
> >        |                     ^~~~~~~~~
> > ../../../../src/include/c.h:918:1: note: in expansion of macro 'pg_noreturn'
> >    918 | pg_noreturn extern void ExceptionalCondition(const char *conditionName,
> >        | ^~~~~~~~~~~
> 
> It's getting confused by _Noreturn, which is defined thus:
> 
> #if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
> #define pg_noreturn _Noreturn
> 
> But apparently on these Solaris-related platforms, g++ defines
> __STDC_VERSION__ even in C++ mode.  (Confirmed in local testing.)
> Apparently, this is even allowed by the C++ standard.

Heh. Pretty odd to do that only on some platforms...


> So the smallest fix is probably to gate this more like this:
> 
> #if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) &&
> !defined(__cplusplus)
> #define pg_noreturn _Noreturn
> 
> (Eventually, we could add support for C++ attributes, but one step at a
> time.)

Makes sense to me.

Greetings,

Andres Freund