ld: rpath not resolved when linking indirect dependencies

Originator:tobias.hahn
Number:rdar://25313838 Date Originated:2016-03-23
Status:Open Resolved:
Product:Developer Tools Product Version:Xcode 7.3 (7D175)
Classification:Serious Bug Reproducible:Always
 
Summary:
When linking indirect dynamic libraries for flat namespace, ld loads all indirect dylibs. If an indirect dylib is linked using an @rpath install name, the linker does not resolve @rpath and produces a "file not found" error.

This is a regression in Xcode 7.3 (ld version ld64-264.3.101), it works as expected using Xcode 7.2.1 (ld version ld64-253.9).

(See the manpage for ld for a description of indirect dynamic libraries.)

Steps to Reproduce:
1. Unzip ld-bug.zip and cd into the directory
2. Run script.sh

Expected Results:
The script runs without error and produces libc.dylib. This is what happens using Xcode 7.2.1.

Actual Results:
The script fails at the last step with the following linker error:
ld: file not found: @rpath/liba.dylib for architecture x86_64

Version:
Mac OS X 10.11.4 / 15E65
Xcode 7.3 / 7D175

Notes:


Configuration:
Mac OS X 10.11.4
Xcode 7.3

Attachments:
'ld-bug.zip' was successfully uploaded.

Comments

It appears that the bug is related to the way ld resolves the library search paths. A possible workaround is to replace '-L.' with '-L./' in OTHER_LDFLAGS. Since the actual linker command line is often generated by a tool such as gyp, cmake etc., this workaround may not be feasible for all use cases.

By tobias.hahn at March 29, 2016, 11:42 a.m. (reply...)

@rpath

We’ve done some analysis of this bug, enough to come up with a horrible workaround, in https://crbug.com/597459.

By mark at March 25, 2016, 9:36 p.m. (reply...)

c.c

void foo_b();
void foo_c();
void foo_c() { foo_b(); }
By tobias.hahn at March 23, 2016, 2:35 p.m. (reply...)

b.c

void foo_a();
void foo_b();
void foo_b() { foo_a(); }
By tobias.hahn at March 23, 2016, 2:35 p.m. (reply...)

a.c

void foo_a();
void foo_a() {}
By tobias.hahn at March 23, 2016, 2:35 p.m. (reply...)

script.sh

#!/bin/bash

clang -c a.c -o a.o
clang -c b.c -o b.o
clang -c c.c -o c.o

LDFLAGS="-dylib -arch x86_64 -macosx_version_min 10.11 -lSystem"
OTHER_LDFLAGS="-L. -flat_namespace -rpath @loader_path/"

ld $LDFLAGS $OTHER_LDFLAGS -dylib_install_name @rpath/liba.dylib -o liba.dylib a.o
ld $LDFLAGS $OTHER_LDFLAGS -dylib_install_name @rpath/libb.dylib -o libb.dylib b.o liba.dylib
ld $LDFLAGS $OTHER_LDFLAGS -dylib_install_name @rpath/libc.dylib -o libc.dylib c.o libb.dylib
By tobias.hahn at March 23, 2016, 2:33 p.m. (reply...)

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