ceff23c6e3
All references to interposable symbols can be redirected at runtime to point to a different symbol definition (with the same name). For example, if both dylib A and B define symbol _foo, and we load A before B at runtime, then all references to _foo within dylib B will point to the definition in dylib A. ld64 makes all extern symbols interposable when linking with `-flat_namespace`. TODO 1: Support `-interposable` and `-interposable_list`, which should just be a matter of parsing those CLI flags and setting the `Defined::interposable` bit. TODO 2: Set Reloc::FinalDefinitionInLinkageUnit correctly with this info (we are currently not setting it at all, so we're erring on the conservative side, but we should help the LTO backend generate more optimal code.) Reviewed By: modimo, MaskRay Differential Revision: https://reviews.llvm.org/D119294
81 lines
3.0 KiB
ArmAsm
81 lines
3.0 KiB
ArmAsm
# REQUIRES: x86
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# RUN: rm -rf %t; split-file %s %t
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## With -flat_namespace, non-weak extern symbols in dylibs become interposable.
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## Check that we generate the correct bindings for them. The test also includes
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## other symbol types like weak externs to verify we continue to do the same
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## (correct) thing even when `-flat_namespace` is enabled, instead of generating
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## spurious bindings.
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/foo.o %t/foo.s
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# RUN: %lld -lSystem -flat_namespace -o %t/foo %t/foo.o
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# RUN: %lld -lSystem -dylib -flat_namespace -o %t/foo.dylib %t/foo.o
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# RUN: %lld -lSystem -bundle -flat_namespace -o %t/foo.bundle %t/foo.o
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# RUN: llvm-objdump --macho --bind --lazy-bind --weak-bind %t/foo | FileCheck \
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# RUN: %s --check-prefix=EXEC --implicit-check-not=_private_extern
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# RUN: llvm-objdump --macho --bind --lazy-bind --weak-bind %t/foo.dylib | \
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# RUN: FileCheck %s --check-prefix=DYLIB --implicit-check-not=_private_extern
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# RUN: llvm-objdump --macho --bind --lazy-bind --weak-bind %t/foo.bundle | \
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# RUN: FileCheck %s --check-prefix=DYLIB --implicit-check-not=_private_extern
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## Executables with -flat_namespace don't have interposable externs.
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# EXEC: Bind table:
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# EXEC-NEXT: segment section address type addend dylib symbol
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# EXEC-EMPTY:
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# EXEC-NEXT: Lazy bind table:
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# EXEC-NEXT: segment section address dylib symbol
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# EXEC-EMPTY:
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# EXEC-NEXT: Weak bind table:
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# EXEC-NEXT: segment section address type addend symbol
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# EXEC-NEXT: __DATA __la_symbol_ptr {{.*}} pointer 0 _weak_extern
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# EXEC-NEXT: __DATA __data {{.*}} pointer 0 _weak_extern
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# EXEC-EMPTY:
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# DYLIB: Bind table:
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# DYLIB-NEXT: segment section address type addend dylib symbol
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# DYLIB-DAG: __DATA __data {{.*}} pointer 0 flat-namespace _extern
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# DYLIB-DAG: __DATA __thread_ptrs {{.*}} pointer 0 flat-namespace _tlv
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# DYLIB-DAG: __DATA_CONST __got {{.*}} pointer 0 flat-namespace dyld_stub_binder
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# DYLIB-EMPTY:
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# DYLIB-NEXT: Lazy bind table:
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# DYLIB-NEXT: segment section address dylib symbol
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# DYLIB-NEXT: __DATA __la_symbol_ptr {{.*}} flat-namespace _extern
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# DYLIB-EMPTY:
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# DYLIB-NEXT: Weak bind table:
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# DYLIB-NEXT: segment section address type addend symbol
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# DYLIB-NEXT: __DATA __la_symbol_ptr {{.*}} pointer 0 _weak_extern
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# DYLIB-NEXT: __DATA __data {{.*}} pointer 0 _weak_extern
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#--- foo.s
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.globl _main, _extern, _weak_extern, _tlv
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.weak_definition _weak_extern
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.private_extern _private_extern
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_extern:
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retq
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_weak_extern:
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retq
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_private_extern:
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retq
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_local:
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retq
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_main:
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callq _extern
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callq _weak_extern
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callq _private_extern
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callq _local
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mov _tlv@TLVP(%rip), %rax
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retq
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.data
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.quad _extern
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.quad _weak_extern
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.quad _local
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.section __DATA,__thread_vars,thread_local_variables
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_tlv:
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.subsections_via_symbols
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