528351 - libffi_msvc doesn't deal with returning structs by value

Status: RESOLVED FIXED

(Core :: js-ctypes, defect)

Description

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js/ctypes/libffi_msvc/win32.c and win64.asm don't implement the entire MSVC ABI. For one, they can't return structs by value. They may also be missing other bits, but I'm not sure.

There have been many updates to libffi's win32 code since libffi_msvc was forked from it in 2003, of which the return-struct-by-value bits was one. We should trawl over them and pick out the relevant bits. Or just re-translate wholesale the gas asm into MSVC asm, as was done originally. (If we can get the libffi build system to work with MSVC, we could maintain this fork inside libffi itself, and have less work to do.)

Until then, I'll have ctypes throw an error when attempting to return a struct by value on MSVC builds. And make sure that the unit tests carefully exercise the important ABI bits that are supported.

Relevant newsgroup thread, bug, and patch:
http://old.nabble.com/-PATCH--Fix-Cygwin-bootstrap,-PR40807-and-all-significant-FAILs-on--win32.-td24612995.html
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40807
http://gcc.gnu.org/viewcvs/trunk/libffi/src/x86/win32.S?r1=150042&r2=150041&pathrev=150042

Comment 1

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Fixed per bug 538216.