On Tuesday, 17 May 2016 at 08:51:01 UTC, Jacob Carlborg wrote:
As an alternative to glibc there's a C standard library called
musl [1]. [...]
The issue is that musl doesn't support the functions defined by
execinfo.h: backtrace, backtrace_symbols_fd and
backtrace_symbols, since these are glibc extensions. As far as
I can see, these functions are used in two places in druntime:
src/rt/backtrace/dwarf.d [3] and src/core/runtime.d [4].
The imports of execinfo is guarded by version(CRuntime_Glibc).
I see that CRuntime_Glibc is a predefined version identifier
defined by the compiler on Linux.
[...]
I just ran into these problems while trying to get D running on a
hardened Gentoo system using musl libc.
Using a patched gdc-4.9.4 I've been able to compile and run a
simple D "Hello world". That made me very happy!
Here are the binaries:
http://www.chadjoan.com/d/gdc-4.9.4-hardened-musl.tar.gz
I have forked the dlang overlay in the hope that it can provide
the necessary information if someone tries to compile the thing
for themselves:
https://github.com/chadjoan/dlang
This is pretty recent work, so I haven't had time to use it for
anything besides "Hello world". I'm also not sure how to run
regression tests for this thing, if there even are any. So this
is all very untested. I'm sharing a minimally useful milestone,
and hopefully it is more than that.
Background:
Earlier, I modified the "dmd-2.067.1-r2" ebuild from the dlang
overlay and actually managed to get it to compile and emit
executables. The BSD execinfo did not even manage to run its own
test program on my system without segfaulting. So I used
libbacktrace for backtraces and had to do a bunch of other
patching to get dmd/druntime/phobos to build on this system; it
involved a lot of trial-and-error. Although it emitted
executables, these executables would segfault or overstep
security bounds enforced by the kernel (to the point where
removing all PAX restrictions would not help it). I remember
something about text relocations, but at this point it's been a
while, so my memory of details is lacking. Diving into codegen
is far too time-consuming in my situation, so that was a dead-end.
I started over with gdc, because I knew that gcc could already
generate working executables on the system. Most of the pain in
this process involved two things: (1) coercing portage into
building gdc in its own directory so that it didn't take over my
system compiler and (2) fixing gcc/gdc build scripts. It was
important to use portage and not just manually configure gdc,
because I wanted to ensure that the resulting gdc build would be
configured and patched in a way closely matching what my system
compiler does (and thus having higher success chances). Trying
to configure and patch it by hand, thus repeating a lot of hard
work already done by Gentoo maintainers, is... not practical. As
for the build scripts: I have no idea what conventions gcc
maintainers use for these things, and thus how I might do basic
things like use an environment variable from outside of the build
process to affect what flags are passed to a compiler. There be
hacks in my patching! As an example, it will unconditionally
compile the D frontend with -fPIC; if you end up building this on
another system and you didn't want that, then it's just too bad
;) So it took more trial-and-error, and maybe a little
compromise, but eventually it got there.
I hope this helps someone.
