Misa cf4511f5d1 Add REMOVE_ABSOLUTE_PATHS CMake option ...

This option is enabled by default and will replace absolute paths of all
source directory file paths with relative paths in the compiled binary,
if the compiler supports it. Of course, this isn't needed if you compile
with all paths removed anyways (e.g. in Release mode).

The purpose is to help make builds reproducible and to remove any
potentially sensitive information about the user or the user's system
from the compiled binary.

Both Clang and GCC support -fdebug-prefix-map, -fmacro-prefix-map, and
-ffile-prefix-map. In particular, -ffile-prefix-map is just a flag that
does both -fdebug-prefix-map and -fmacro-prefix-map.

According to https://reproducible-builds.org/docs/build-path/ ,
-fdebug-prefix-map is available in all GCC versions but only available
starting from Clang 3.8, and -fmacro-prefix-map and -ffile-prefix-map
are available since GCC 8 and Clang 10. So we check the compiler version
and use the available flags depending on if the compiler supports it or
not.

This does make debugging a bit more annoying, but there are a couple
ways to rectify this. Either disable it with
-DREMOVE_ABSOLUTE_PATHS=OFF, or add a `.gdbinit` that consists of

    set substitute-path . ../..

so that `.` is considered to be `../..`. Of course, if you need to,
replace `../..` with the actual source directory path (in my case it's
`../../..` because I place my build folders in another subdirectory to
have multiple build folders in one directory).

This doesn't need to be a global `.gdbinit`, it can be in a
directory-specific `.gdbinit` (similar to how `.gitignore`s can also be
directory-specific). But then you need to add `add-auto-load-safe-path`
to your `.gdbinit` to load any directory-specific `.gdbinit`s.

The above is for GDB; I don't know what (if anything) needs to be done
for LLDB; I don't use LLDB.

Fixes #889.

2022-08-21 15:31:11 -07:00

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