[Bug go/72814] reflect FAILs on 32-bit Solaris/SPARC: SIGILL

[ian at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72814

--- Comment #2 from ian at gcc dot gnu.org <ian at gcc dot gnu.org> ---
Author: ian
Date: Mon Aug  8 19:53:44 2016
New Revision: 239252

URL: https://gcc.gnu.org/viewcvs?rev=239252&root=gcc&view=rev
Log:
        PR go/72814

    runtime: treat zero-sized result value as void

    Change the FFI interface to treat a call to a function that returns a
    zero-sized result as a call to a function that returns void.

    This is part of the fix for https://gcc.gnu.org/PR72814.  On 32-bit
    SPARC systems, a call to a function that returns a non-zero-sized struct
    is followed by an unimp instruction that describes the size of the
    struct.  The function returns to the address after the unimp
    instruction.  The libffi library can not represent a zero-sized struct,
    so we wind up treating it as a 1-byte struct.  Thus in that case libffi
    calls the function with an unimp instruction, but the function does not
    adjust the return address.  The result is that the program attempts to
    execute the unimp instruction, causing a crash.

    This is part of a change that fixes the crash by treating all functions
    that return zero bytes as functions that return void.

    Reviewed-on: https://go-review.googlesource.com/25585

        * go-gcc.cc (Gcc_backend::function_type): If the return type is
        zero bytes, treat the function as returning void.
        (return_statement): If the return type is zero bytes, don't
        actually return any values.

Modified:
    trunk/gcc/go/ChangeLog
    trunk/gcc/go/go-gcc.cc
    trunk/gcc/go/gofrontend/MERGE
    trunk/libgo/runtime/go-ffi.c