Re: Bignum speedup patch causes crash at startup

[Paul Eggert]

Andy Moreton wrote:
> I now see a strange warning on 64bit Windows (building with gcc 8.2.0
> for target x86_64-w64-mingw32):
>
>    CC       data.o
> In file included from C:/emacs/git/emacs/master/src/data.c:31:
> C:/emacs/git/emacs/master/src/data.c: In function 'arith_driver':
> C:/emacs/git/emacs/master/src/lisp.h:2479:34: warning: 'accum' may be used 
> uninitialized in this function [-Wmaybe-uninitialized]
>     return FIXNUM_OVERFLOW_P (n) ? make_bigint (n) : make_fixnum (n);
>                                    ^~~~~~~~~~~~~~~
> C:/emacs/git/emacs/master/src/data.c:2962:12: note: 'accum' was declared here
>     intmax_t accum = XFIXNUM (val);

GCC complains that 'accum' might be used uninitialized even though 'accum's 
declaration has an initializer? Looks like a clear GCC bug, and might be worth 
reporting there.

For what it's worth I don't observe the problem on RHEL 7 x86-64, building with 
GCC 8.2.0 (which I built myself for x86_64-pc-linux-gnu) and configuring Emacs 
with './configure --enable-gcc-warnings --with-gif=no'.