From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: pgsql-hackers@lists.postgresql.org
Subject: tableam.h fails cpluspluscheck
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Date: Thu, 30 May 2019 14:01:00 -0400
Message-ID: <53941.1559239260@sss.pgh.pa.us>
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Using Apple's clang as c++ compiler:

In file included from /tmp/cpluspluscheck.KejiIw/test.cpp:3:
./src/include/access/tableam.h:144:16: error: typedef redefinition with di=
fferent types ('void (*)(Relation, HeapTuple, Datum *, bool *, bool, void =
*)' (aka 'void (*)(RelationData *, HeapTupleData *, unsigned long *, bool =
*, bool, void *)') vs 'IndexBuildCallback')
typedef void (*IndexBuildCallback) (Relation index,
               ^
./src/include/access/tableam.h:36:8: note: previous definition is here
struct IndexBuildCallback;
       ^

(there are some cascading errors, but this is the important one)

Kinda looks like you can't get away with using "struct" on a forward
declaration of something that is not actually a struct type.

			regards, tom lane