Re: [PATCH 0/9] Add UBSan to the build

[Tom Tromey <tom at tromey dot com>]

>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> Might be noticeable in "make check" time.
Pedro> If you're doing performance analysis, say, running "make check-perf", or running
Pedro> some use case under "perf", sounds like you'll need to be sure to
Pedro> disable UBSan.  I also mildly worry about random people comparing the
Pedro> performance of master GDB or some ftp snapshot against previous GDB versions
Pedro> or against other debuggers and being mislead.  If that slowdown is true, I think we
Pedro> should at least document it somewhere more prominently, as I think that so
Pedro> far release vs development mode didn't have much of an impact?

Anyone doing performance analysis really must compile with -O2 and
disable all the checking.  It really does matter, IIRC the sleb/uleb
decoders really suffer without optimization.

Pedro> Kind of like how GCC documents --enable-checking, at
Pedro> <https://gcc.gnu.org/install/configure.html>:

Pedro> "When you specify this option, the compiler is built to perform internal consistency
Pedro> checks of the requested complexity. This does not change the generated code, but adds
Pedro> error checking within the compiler. This will slow down the compiler and may only work
Pedro> properly if you are building the compiler with GCC. This is ‘yes,extra’ by default when
Pedro> building from SVN or snapshots, but ‘release’ for releases."

Do we have a similar doc somewhere?  I could update it.
Also I think this series should update NEWS for the new configure option.

Tom