NB: The crossposting is actually suggested on the mailing list description: "If you've found a bug in PostgreSQL, please send it both to this list and also to the pgsql-patches list."
Amd64 and powerpc share an ABI design which enables variable passing in registers and which makes va_list a complex datatype. Due to gcc not implementing a part of the C9x standard (http://mail-index.netbsd.org/tech-toolchain/2003/11/11/0011.html) taking a pointer to a va_list will fail on these platforms. The corresponding bug (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=8262) is closed, so the gcc developers seem not to plan to change this.
So I propose the following hack (feel free to improve it!) to go into mainline. Since only powerpc and amd64 are affected (and the old method does not work at all here at all) the patch should not be controversial.
PS: I don't know about other architectures. I can't believe that only ppc and amd64 pass parameters in registers. PPS: I could not test it on amd64, but all docs indicate the same behaviour.
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