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Date: Thu, 19 Feb 2026 09:31:45 +0100
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Subject: Re: Make copyObject work in C++
To: Jelte Fennema-Nio <postgres@jeltef.nl>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
 Thomas Munro <thomas.munro@gmail.com>
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From: Peter Eisentraut <peter@eisentraut.org>
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On 13.02.26 11:28, Jelte Fennema-Nio wrote:
> Patch 3 makes copyObject work when using GCC or Clang with -std=c++11 by
> introducing pg_exprtype.
> 
> Patch 4 starts using pg_exprtype in more places.

I found this paper

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2927.htm

which led to the addition of typeof into the C standard.

It contains a section 'Why not "decltype"?' that explains how decltype 
is different, but it also explains that if typeof were added to C++, 
then it would be

     std::remove_reference_t<decltype(T)>

What I suggest we should do here is:

1. Add a configure test that checks if the C++ compiler supports typeof.

2. If not, #define typeof to the above expression.

Then code can continue to use typeof unchanged.