I have a build of GHC (with DYNAMIC_GHC_PROGRAMS=NO) that exhibits the following crash:

  $ ghc -e 'System.Environment.getEnvironment'
  <segfault>

I tracked it down, eventually, to a bad reference to the symbol environ from __hscore_environ in libraries/base/includes/HsBase.h. Somehow, environ had got linked to the wrong address.

Lots more investigation lead me to discover this: internal_dlsym() in Linker.c tries to look up a symbol in all the different shared libraries we have loaded so far, one by one. (see be497c20). Unfortunately, this seems to break things in my case. Here's a simple test program that works on Ubuntu 12.04:

#include <dlfcn.h>
#include <stdio.h>

char *so = "/usr/lib/x86_64-linux-gnu/libgmp.so";
char *so2 = "/usr/lib/x86_64-linux-gnu/libpthread.so";

extern char**environ;

int main(int argc, char *argv[])
{
  void *deflt, *hdl;
  deflt = dlopen(NULL, RTLD_LAZY | RTLD_GLOBAL);
  printf("environ = %p\n", &environ);
  printf("dlsym(deflt, \"environ\") = %p\n", dlsym(deflt,"environ"));
  hdl = dlopen(so, RTLD_LAZY);
  printf("dlsym(\"libgmp\", \"environ\") = %p\n", dlsym(hdl,"environ"));
  hdl = dlopen(so2, RTLD_LAZY);
  printf("dlsym(\"libpthread\", \"environ\") = %p\n", dlsym(hdl,"environ"));
}

And the output:

environ = 0x601040
dlsym(deflt, "environ") = 0x601040
dlsym("libgmp", "environ") = 0x2aaaab290568
dlsym("libpthread", "environ") = 0x601040

Note that the value we get from looking up environ in libgmp is different to the others. The correct value is 0x601040. gdb thinks that 0x2aaaab290568 is also environ:

(gdb) p4 0x2aaaab290568
0x2aaaab290580 <buflen.9817>:   0x0
0x2aaaab290578: 0x0
0x2aaaab290570 <miss_F_GETOWN_EX>:      0x0
0x2aaaab290568 <environ>:       0x0

but note that it contains zero. The real one is:

(gdb) p4 0x601040
0x601058:       0x0
0x601050 <dtor_idx.6533>:       0x0
0x601048 <completed.6531>:      0x0
0x601040 <environ@@GLIBC_2.2.5>:        0x7fffffffe268

In GHC we're loading libgmp when we load the integer-gmp package, and this causes future references to environ to go wrong.

I've locally fixed this by changing internal_dlsym to dlsym, but since there was a reason to make this change in the first place I haven't pushed it to master. Suggestions welcome.