Re: clisp -Wshift-negative-value on

[Bruno H. <br...@cl...>]

Hi Sam,

> ../src/debug.d:571:7: warning: shifting a negative signed value is undefined
>       [-Wshift-negative-value]
>
> $ gcc --version
> Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/usr/include/c++/4.2.1
> Apple LLVM version 8.0.0 (clang-800.0.42.1)

http://stackoverflow.com/questions/3784996/why-does-left-shift-operation-invoke-undefined-behaviour-when-the-left-side-oper
does not give me any insight about the real reasons of the warning.

Generally, some operations on signed integers now give undefined behaviour,
and some compilers like GCC exploit this. So, it is nowadays generally wiser
to do bit manipulations only on unsigned integers. I guess it will be a lot
of work to revisit clisp's code in this direction. The first step towards
this is to pick the relevant warnings. So far, I'd guess that
-Wshift-negative-value is not among the relevant warnings.

Bruno