paulp · August 29, 2015 14:22 · May 29, 2015 · May 29, 2015 · May 29, 2015
diff --git a/03-fallback-collision-example.sh → 02-fallback-collision-example.sh b/03-fallback-collision-example.sh → 02-fallback-collision-example.sh
@@ -1,4 +1,4 @@
-# DYLD_FALLBACK_LIBRARY_PATH also breaks library path resolution when you have two applications that
+# DYLD_FALLBACK_LIBRARY_PATH breaks library path resolution when you have two applications that
 # have a library name collision and use DYLD_* varibles to force dyld to find their libraries -- a
 # use-case that would work without error when using proper install name/@rpath Mach-O linking.
 mkdir rust-lib

diff --git a/02-fallback-weak-link-example.sh → 03-fallback-weak-link-example.sh b/02-fallback-weak-link-example.sh → 03-fallback-weak-link-example.sh
@@ -1,5 +1,5 @@
-# DYLD_FALLBACK_LIBRARY_PATH library variables will also break weak linking of libraries that would
-# otherwise succeed when using proper Mach-O install names.
+# DYLD_FALLBACK_LIBRARY_PATH library variables can also break weak linking of libraries if 1) the weakly linked
+# library is not found, and 2) a fallback path contains an incompatible library.
 #
 # Assume a library weakly linked by a third-party library. If the library is not found, but a similarly named library
 # is found in DYLD_FALLBACK_LIBRARY_PATH, dyld will attempt to use that (incorrect) library.

diff --git a/name-collision-example.sh → 01-name-collision-example.sh b/name-collision-example.sh → 01-name-collision-example.sh
diff --git a/fallback-weak-link-example.sh → 02-fallback-weak-link-example.sh b/fallback-weak-link-example.sh → 02-fallback-weak-link-example.sh
diff --git a/fallback-collision-example.sh → 03-fallback-collision-example.sh b/fallback-collision-example.sh → 03-fallback-collision-example.sh
diff --git a/fallback-collision-example.sh b/fallback-collision-example.sh
@@ -0,0 +1,18 @@
+# DYLD_FALLBACK_LIBRARY_PATH also breaks library path resolution when you have two applications that
+# have a library name collision and use DYLD_* varibles to force dyld to find their libraries -- a
+# use-case that would work without error when using proper install name/@rpath Mach-O linking.
+mkdir rust-lib
+mkdir mathematica-lib
+echo 'void my_libjpeg_api (void) { }' | clang -dynamiclib -x objective-c -o rust-lib/libjpeg.dylib -install_name libjpeg.dylib -
+clang -dynamiclib -x objective-c -o mathematica-lib/libjpeg.dylib -install_name libjpeg.dylib - < /dev/null
+
+echo 'extern void my_libjpeg_api(void); int main (int argc, char *argv[]) { my_libjpeg_api(); return 0; }' | clang -x objective-c -o example - -framework ImageIO -Lrust-lib -ljpeg
+env DYLD_FALLBACK_LIBRARY_PATH=`pwd`/mathematica-lib:`pwd`/rust-lib ./example
+
+#dyld: lazy symbol binding failed: Symbol not found: _my_libjpeg_api
+#  Referenced from: /private/tmp/./example
+#  Expected in: /tmp/mathematica-lib/libjpeg.dylib
+#
+#dyld: Symbol not found: _my_libjpeg_api
+#  Referenced from: /private/tmp/./example
+#  Expected in: /tmp/mathematica-lib/libjpeg.dylib
diff --git a/fallback-weak-link-example.sh b/fallback-weak-link-example.sh
@@ -0,0 +1,31 @@
+# DYLD_FALLBACK_LIBRARY_PATH library variables will also break weak linking of libraries that would
+# otherwise succeed when using proper Mach-O install names.
+#
+# Assume a library weakly linked by a third-party library. If the library is not found, but a similarly named library
+# is found in DYLD_FALLBACK_LIBRARY_PATH, dyld will attempt to use that (incorrect) library.
+mkdir rust-lib
+mkdir third-party-lib
+
+# Create a 'libthird_party.dylib' library that weakly links to a 'libcommon_libname.dylib'
+echo 'void my_weak_api (void) { }' | clang -dynamiclib -x objective-c -o third-party-lib/libcommon_libname.dylib -
+echo 'extern void my_weak_api (void); void my_weak_api_caller (void) { if (my_weak_api) my_weak_api(); }' | clang -dynamiclib -x objective-c -o third-party-lib/libthird_party.dylib -weak_library third-party-lib/libcommon_libname.dylib -
+
+# Remove the weakly linked library; we're pretending that it's not available on this install, a possibility
+# that led us to weakly link it in the first place.
+rm third-party-lib/libcommon_libname.dylib
+
+# Create a conflictingly-named 'libcommon_libname.dylib' library
+clang -dynamiclib -x objective-c -o rust-lib/libcommon_libname.dylib - < /dev/null
+
+# Link our binary against libthird_party.dylib
+echo 'extern void my_weak_api_caller(void); int main (int argc, char *argv[]) { my_weak_api_caller(); return 0; }' | clang -x objective-c -o example - -Lthird-party-lib -lthird_party
+
+env DYLD_FALLBACK_LIBRARY_PATH=`pwd`/rust-lib ./example
+
+#dyld: lazy symbol binding failed: Symbol not found: _my_weak_api
+#  Referenced from: third-party-lib/libthird_party.dylib
+#  Expected in: /tmp/rust-lib/libcommon_libname.dylib
+
+#dyld: Symbol not found: _my_weak_api
+#  Referenced from: third-party-lib/libthird_party.dylib
+#  Expected in: /tmp/rust-lib/libcommon_libname.dylib
diff --git a/name-collision-example.sh b/name-collision-example.sh
@@ -0,0 +1,11 @@
+# DYLD_LIBRARY_PATH library variables break linking of standard system libraries by forcing dyld to ignore
+# everything but the library's basename when performing what would otherwise be successful library
+# resolution.
+mkdir rust-lib
+echo 'void my_libjpeg_api (void) { }' | clang -dynamiclib -x objective-c -o rust-lib/libjpeg.dylib -
+echo 'extern void my_libjpeg_api(void); int main (int argc, char *argv[]) { my_libjpeg_api(); return 0; }' | clang -x objective-c -o example - -framework ImageIO -Lrust-lib -ljpeg
+env DYLD_LIBRARY_PATH=`pwd`/rust-lib ./example
+
+#dyld: Library not loaded: /System/Library/Frameworks/ImageIO.framework/Versions/A/Resources/libJPEG.dylib
+#  Referenced from: /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO
+#  Reason: Incompatible library version: ImageIO requires version 1.0.0 or later, but libjpeg.dylib provides version 0.0.0