Issue 1:
Using/calling a variable defined as a BigFloat literal (ie. a = big"1.0") will cause a seg fault (and consequently crash julia) in a precompiled module, but the two other methods of defining BigFloats that I am aware of, b = BigFloat(1.0) and parse(BigFloat,"1.0") do not cause the seg fault.

This is the smallest code that will reproduce the issue:

__precompile__()

module Global_bigfloat_literal

export a,b,c,d

function __init__()
global const a = big"28.0"
global const b = 10.0
global const c = BigFloat(28.0)
global const d = parse(BigFloat,"2.6666666666666666666666666666666666666666666666666666666666666666666666666666666")
end

end

Output of above code:

julia> b
28.0

julia> c
2.800000000000000000000000000000000000000000000000000000000000000000000000000000e+01

julia> d
2.666666666666666666666666666666666666666666666666666666666666666666666666666678

julia> a

signal (11): Segmentation fault
while loading no file, in expression starting on line 0
__gmpn_mul_basecase at /usr/bin/../lib/x86_64-linux-gnu/libgmp.so (unknown line)
mpfr_get_str at /usr/lib/x86_64-linux-gnu/libmpfr.so.4 (unknown line)
unknown function (ip: 0x7facfaa0f8e3)
__gmpfr_vasprintf at /usr/lib/x86_64-linux-gnu/libmpfr.so.4 (unknown line)
mpfr_snprintf at /usr/lib/x86_64-linux-gnu/libmpfr.so.4 (unknown line)
string at ./mpfr.jl:857
show at ./mpfr.jl:869 [inlined]
show at ./replutil.jl:4 [inlined]
display at ./REPL.jl:132
unknown function (ip: 0x7facec00c476)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
display at ./REPL.jl:135
unknown function (ip: 0x7facec00c186)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
display at ./multimedia.jl:143
unknown function (ip: 0x7facec00bfc2)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
print_response at ./REPL.jl:154
unknown function (ip: 0x7facec008bf8)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
print_response at ./REPL.jl:139
unknown function (ip: 0x7facec008648)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
#22 at ./REPL.jl:652
unknown function (ip: 0x7facebfffd11)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
run_interface at ./LineEdit.jl:1579
unknown function (ip: 0x7faefd93639f)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
run_frontend at ./REPL.jl:903
run_repl at ./REPL.jl:188
unknown function (ip: 0x7facebff7532)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
_start at ./client.jl:363
unknown function (ip: 0x7faefd9512c8)
jl_call_method_internal at ./src/./src/julia_internal.h:211 [inlined]
jl_apply_generic at ./src/./src/gf.c:1950
unknown function (ip: 0x5616362c4a8c)
unknown function (ip: 0x5616362c4356)
__libc_start_main at /build/glibc-cxyGtm/glibc-2.24/csu/../csu/libc-start.c:291
unknown function (ip: 0x5616362c43a9)
Allocations: 1722872 (Pool: 1721994; Big: 878); GC: 0

Version info:

Julia Version 0.5.2

Commit f4c6c9d (2017-05-06 16:34 UTC)

Platform Info:

OS: Linux (x86_64-linux-gnu)

CPU: Intel(R) Core(TM) i3-2370M CPU @ 2.40GHz

WORD_SIZE: 64

BLAS: libopenblas (NO_LAPACKE DYNAMIC_ARCH NO_AFFINITY Sandybridge)

LAPACK: liblapack.so.3

LIBM: libopenlibm

LLVM: libLLVM-3.7.1 (ORCJIT, sandybridge)

I have also tested that this is an issue in Windows (it is).

Issue 2:
__precompile__()
module Crash
const x = big"123"
__init__() = @show x
end # module

julia> using Crash
INFO: Precompiling module Crash...

signal (11): Segmentation fault
while loading no file, in expression starting on line 0
__gmpz_get_str at /home/ubuntu/julia-debugger/usr/bin/../lib/libgmp.so (unknown line)
base at ./gmp.jl:518
[inline] at ./gmp.jl:509
showall at ./show.jl:1428