https://llvm.org/bugs/show_bug.cgi?id=27194
Bug ID: 27194
Summary: lld segfaults linking mach on linux
Product: lld
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: All Bugs
Assignee: unassignedb...@nondot.org
Reporter: m4b.github...@gmail.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
I'm trying to cross compile a binary (in this case an object file generated by
Rust) on GNU/Linux to the x86_64-apple-darwin target, so I could be doing
something stupid here (nevertheless the bug which is an unchecked null pointer
dereference should probably be fixed/checked).
But assuming I have the macho object file, call it main.0.o, and darwin system
libraries, imagine we have something like the following script:
```
#!/bin/bash
DIR=/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib
DARWIN_PATH=/home/m4b/binaries/darwin/usr/lib
SYS=$DARWIN_PATH/system
LLD=/home/m4b/Downloads/llvm-3.8.0.src/build/bin/lld
$LLD -flavor darwin -Z -arch x86_64 -t -L
"/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib"
"$SYS/libsystem_platform.dylib" "$SYS/libsystem_c.dylib"
"$SYS/libsystem_pthread.dylib" "$SYS/libunwind.dylib" "$SYS/libdyld.dylib"
"$DIR/liblibc-18402db3.rlib" -lcompiler-rt "$DIR/libstd-18402db3.dylib"
"$DIR/libcollections-18402db3.rlib" "$DIR/librustc_unicode-18402db3.rlib"
"$DIR/librand-18402db3.rlib" "$DIR/liballoc-18402db3.rlib"
"$DIR/liballoc_jemalloc-18402db3.rlib" "$DIR/libcore-18402db3.rlib"
"$DIR/libcompiler-rt.a" main.0.o -o main_apple
```
I provide paths to the darwin shared objects and rust libs which provide the
necessary symbols for main.0.o (and no reexporting libs, otherwise we die on an
assertion because obviously it won't find the exporting binary in the right
place on my linux system).
Unfortunately however, lld segfaults in `CompactUnwindPass.cpp` due to the
`dyn_cast` returning null and not being checked in the next line, e.g. at line
509:
```
const DefinedAtom *cfiTarget = dyn_cast<DefinedAtom>(ref->target());
if (cfiTarget->contentType() == DefinedAtom::typeCFI)
```
Why it's null I don't know :/
The full output is:
/home/m4b/binaries/darwin/usr/lib/system/libsystem_platform.dylib
/home/m4b/binaries/darwin/usr/lib/system/libsystem_c.dylib
/home/m4b/binaries/darwin/usr/lib/system/libsystem_pthread.dylib
/home/m4b/binaries/darwin/usr/lib/system/libunwind.dylib
/home/m4b/binaries/darwin/usr/lib/system/libdyld.dylib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liblibc-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcompiler-rt.a
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libstd-18402db3.dylib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcollections-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/librustc_unicode-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/librand-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liballoc-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liballoc_jemalloc-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcore-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcompiler-rt.a
t.0.o
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcore-18402db3.rlib(core-18402db3.0.o)
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liballoc_jemalloc-18402db3.rlib(alloc_jemalloc-18402db3.0.o)
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liballoc-18402db3.rlib(alloc-18402db3.0.o)
0 lld 0x00000000004ffc8d
1 lld 0x000000000050000a
2 lld 0x00000000004fe768
3 lld 0x00000000004ff78c
4 libpthread.so.0 0x00007fda7187ee80
5 lld 0x0000000001ec80ae
6 lld 0x0000000001ecc2ca
7 lld 0x000000000041fdb4
8 lld 0x000000000041e6d3
9 lld 0x000000000041434a
10 lld 0x000000000040d915
11 lld 0x000000000040c958
12 libc.so.6 0x00007fda70a3a710 __libc_start_main + 240
13 lld 0x000000000040c819
Stack dump:
0. Program arguments: /usr/bin/lld -Z -arch x86_64 -t -L
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib
/home/m4b/binaries/darwin/usr/lib/system/libsystem_platform.dylib
/home/m4b/binaries/darwin/usr/lib/system/libsystem_c.dylib
/home/m4b/binaries/darwin/usr/lib/system/libsystem_pthread.dylib
/home/m4b/binaries/darwin/usr/lib/system/libunwind.dylib
/home/m4b/binaries/darwin/usr/lib/system/libdyld.dylib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liblibc-18402db3.rlib
-lcompiler-rt
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libstd-18402db3.dylib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcollections-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/librustc_unicode-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/librand-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liballoc-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/liballoc_jemalloc-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcore-18402db3.rlib
/home/m4b/.multirust/toolchains/nightly/lib/rustlib/x86_64-apple-darwin/lib/libcompiler-rt.a
main.0.o -o main_apple -flavor darwin
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