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llvm-project/lld/test/MachO/private-extern.s

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[lld/mac] Implement support for private extern symbols Private extern symbols are used for things scoped to the linkage unit. They cause duplicate symbol errors (so they're in the symbol table, unlike TU-scoped truly local symbols), but they don't make it into the export trie. They are created e.g. by compiling with -fvisibility=hidden. If two weak symbols have differing privateness, the combined symbol is non-private external. (Example: inline functions and some TUs that include the header defining it were built with -fvisibility-inlines-hidden and some weren't). A weak private external symbol implicitly has its "weak" dropped and behaves like a regular strong private external symbol: Weak is an export trie concept, and private symbols are not in the export trie. If a weak and a strong symbol have different privateness, the strong symbol wins. If two common symbols have differing privateness, the larger symbol wins. If they have the same size, the privateness of the symbol seen later during the link wins (!) -- this is a bit lame, but it matches ld64 and this behavior takes 2 lines less to implement than the less surprising "result is non-private external), so match ld64. (Example: `int a` in two .c files, both built with -fcommon, one built with -fvisibility=hidden and one without.) This also makes `__dyld_private` a true TU-local symbol, matching ld64. To make this work, make the `const char*` StringRefZ ctor to correctly set `size` (without this, writing the string table crashed when calling getName() on the __dyld_private symbol). Mention in CommonSymbol's comment that common symbols are now disabled by default in clang. Mention in -keep_private_externs's HelpText that the flag only has an effect with `-r` (which we don't implement yet -- so this patch here doesn't regress any behavior around -r + -keep_private_externs)). ld64 doesn't explicitly document it, but the commit text of http://reviews.llvm.org/rL216146 does, and ld64's OutputFile::buildSymbolTable() checks `_options.outputKind() == Options::kObjectFile` before calling `_options.keepPrivateExterns()` (the only reference to that function). Fixes PR48536. Differential Revision: https://reviews.llvm.org/D93609
2020-12-18 02:30:18 +08:00
# REQUIRES: x86
# RUN: split-file %s %t
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/basics.s -o %t/basics.o
## Check that .private_extern symbols are marked as local in the symbol table
## and aren't in the export trie.
# RUN: %lld -dylib %t/basics.o -o %t/basics
# RUN: llvm-objdump --syms --exports-trie %t/basics | \
# RUN: FileCheck --check-prefix=EXPORTS %s
# RUN: llvm-nm -m %t/basics | FileCheck --check-prefix=EXPORTS-NM %s
# EXPORTS-LABEL: SYMBOL TABLE:
# EXPORTS-DAG: [[#%x, FOO_ADDR:]] l {{.*}} _foo
# EXPORTS-DAG: [[#%x, BAR_ADDR:]] g {{.*}} _bar
# EXPORTS-LABEL: Exports trie:
# EXPORTS-NOT: 0x{{0*}}[[#%X, FOO_ADDR]] _foo
# EXPORTS-DAG: 0x{{0*}}[[#%X, BAR_ADDR]] _bar
# EXPORTS-NOT: 0x{{0*}}[[#%X, FOO_ADDR]] _foo
# EXPORTS-NM-DAG: (__TEXT,__cstring) non-external (was a private external) _foo
# EXPORTS-NM-DAG: (__TEXT,__cstring) external _bar
#--- basics.s
.section __TEXT,__cstring
.globl _foo, _bar
.private_extern _foo
_foo:
.asciz "Foo"
_bar:
.asciz "Bar"
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/strong-globl.s -o %t/strong-globl.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/weak-globl.s -o %t/weak-globl.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/strong-private.s -o %t/strong-private.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/weak-private.s -o %t/weak-private.o
## weak + strong symbol takes privateness from strong symbol
## - weak private extern + strong extern = strong extern (for both .o orderings)
# RUN: %lld -dylib %t/weak-private.o %t/strong-globl.o -o %t/wpsg
# RUN: llvm-nm -m %t/wpsg | FileCheck --check-prefix=EXTERNAL %s
# RUN: %lld -dylib %t/strong-globl.o %t/weak-private.o -o %t/sgwp
# RUN: llvm-nm -m %t/sgwp | FileCheck --check-prefix=EXTERNAL %s
# EXTERNAL: (__TEXT,__text) external _foo
## - weak extern + strong private extern = strong private extern
## (for both .o orderings)
# RUN: %lld -dylib %t/weak-globl.o %t/strong-private.o -o %t/wgsp
# RUN: llvm-nm -m %t/wgsp | FileCheck --check-prefix=NONEXTERNAL %s
# RUN: %lld -dylib %t/strong-private.o %t/weak-globl.o -o %t/spwg
# RUN: llvm-nm -m %t/spwg | FileCheck --check-prefix=NONEXTERNAL %s
# NONEXTERNAL: (__TEXT,__text) non-external (was a private external) _foo
## weak + weak symbol take weaker privateness
## - weak extern + weak private extern = weak extern (both orders)
# RUN: %lld -dylib %t/weak-private.o %t/weak-globl.o -o %t/wpwg
# RUN: llvm-nm -m %t/wpwg | FileCheck --check-prefix=WEAK-EXTERNAL %s
# RUN: %lld -dylib %t/weak-globl.o %t/weak-private.o -o %t/wgwp
# RUN: llvm-nm -m %t/wgwp | FileCheck --check-prefix=WEAK-EXTERNAL %s
# WEAK-EXTERNAL: (__TEXT,__text) weak external _foo
## - weak private extern + weak private extern = weak private extern
# RUN: %lld -dylib %t/weak-private.o %t/weak-private.o -o %t/wpwp
# RUN: llvm-nm -m %t/wpwp | FileCheck --check-prefix=NONEXTERNAL %s
#--- strong-globl.s
.globl _foo
_foo:
retq
#--- weak-globl.s
.globl _foo
.weak_definition _foo
_foo:
retq
#--- strong-private.s
.private_extern _foo
.globl _foo
_foo:
retq
#--- weak-private.s
.private_extern _foo
.globl _foo
.weak_definition _foo
_foo:
retq
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/comm-small.s -o %t/comm-small.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/comm-large.s -o %t/comm-large.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/comm-small-private.s -o %t/comm-small-private.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
# RUN: %t/comm-large-private.s -o %t/comm-large-private.o
## For common symbols the larger one wins.
## - smaller private extern + larger extern = larger extern
# RUN: %lld -dylib %t/comm-small-private.o %t/comm-large.o -o %t/cspcl
# RUN: llvm-nm -m %t/cspcl | FileCheck --check-prefix=COMMON-EXTERNAL %s
# RUN: %lld -dylib %t/comm-large.o %t/comm-small-private.o -o %t/clcsp
# RUN: llvm-nm -m %t/clcsp | FileCheck --check-prefix=COMMON-EXTERNAL %s
# COMMON-EXTERNAL: (__DATA,__common) external _foo
## - smaller extern + larger private extern = larger private extern
# RUN: %lld -dylib %t/comm-large-private.o %t/comm-small.o -o %t/clpcs
# RUN: llvm-nm -m %t/clpcs | FileCheck --check-prefix=COMMON-NONEXTERNAL %s
# RUN: %lld -dylib %t/comm-small.o %t/comm-large-private.o -o %t/csclp
# RUN: llvm-nm -m %t/csclp | FileCheck --check-prefix=COMMON-NONEXTERNAL %s
# COMMON-NONEXTERNAL: (__DATA,__common) non-external (was a private external) _foo
# For common symbols with the same size, the privateness of the symbol seen
# later wins (!).
## - equal private extern + equal extern = equal extern (both orders)
# RUN: %lld -dylib %t/comm-small-private.o %t/comm-small.o -o %t/cspcs
# RUN: llvm-nm -m %t/cspcs | FileCheck --check-prefix=COMMON-EXTERNAL %s
## - equal extern + equal private extern = equal private extern (both orders)
# RUN: %lld -dylib %t/comm-small.o %t/comm-small-private.o -o %t/cscsp
# RUN: llvm-nm -m %t/cscsp | FileCheck --check-prefix=COMMON-NONEXTERNAL %s
## - equal private extern + equal private extern = equal private extern
# RUN: %lld -dylib %t/comm-small-private.o %t/comm-small-private.o -o %t/cspcsp
# RUN: llvm-nm -m %t/cspcsp | FileCheck --check-prefix=COMMON-NONEXTERNAL %s
#--- comm-small.s
.comm _foo,4,2
#--- comm-large.s
.comm _foo,8,3
#--- comm-small-private.s
.private_extern _foo
.comm _foo,4,2
#--- comm-large-private.s
.private_extern _foo
.comm _foo,8,3