[lld] r330788 - Bring r329960 back.
Rafael Espindola via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 24 17:29:13 PDT 2018
Author: rafael
Date: Tue Apr 24 17:29:13 2018
New Revision: 330788
URL: http://llvm.org/viewvc/llvm-project?rev=330788&view=rev
Log:
Bring r329960 back.
The fix is to copy Used when replacing the symbol.
Original message:
Do not keep shared symbols created from garbage-collected eliminated DSOs.
If all references to a DSO happen to be weak, and if the DSO is
specified with --as-needed, the DSO is not added to DT_NEEDED.
If that happens, we also need to eliminate shared symbols created
from the DSO. Otherwise, they become dangling references that point
to non-exsitent DSO.
Fixes https://bugs.llvm.org/show_bug.cgi?id=36991
Differential Revision: https://reviews.llvm.org/D45536
Added:
lld/trunk/test/ELF/as-needed-weak.s
Modified:
lld/trunk/ELF/Driver.cpp
lld/trunk/test/ELF/gc-sections-shared.s
Modified: lld/trunk/ELF/Driver.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=330788&r1=330787&r2=330788&view=diff
==============================================================================
--- lld/trunk/ELF/Driver.cpp (original)
+++ lld/trunk/ELF/Driver.cpp Tue Apr 24 17:29:13 2018
@@ -1119,6 +1119,23 @@ template <class ELFT> static void handle
Symtab->fetchLazy<ELFT>(Sym);
}
+// If all references to a DSO happen to be weak, the DSO is not added
+// to DT_NEEDED. If that happens, we need to eliminate shared symbols
+// created from the DSO. Otherwise, they become dangling references
+// that point to a non-existent DSO.
+template <class ELFT> static void demoteSharedSymbols() {
+ for (Symbol *Sym : Symtab->getSymbols()) {
+ if (auto *S = dyn_cast<SharedSymbol>(Sym)) {
+ if (!S->getFile<ELFT>().IsNeeded) {
+ bool Used = S->Used;
+ replaceSymbol<Undefined>(S, nullptr, S->getName(), STB_WEAK, S->StOther,
+ S->Type);
+ S->Used = Used;
+ }
+ }
+ }
+}
+
// Do actual linking. Note that when this function is called,
// all linker scripts have already been parsed.
template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
@@ -1279,6 +1296,7 @@ template <class ELFT> void LinkerDriver:
// Do size optimizations: garbage collection, merging of SHF_MERGE sections
// and identical code folding.
markLive<ELFT>();
+ demoteSharedSymbols<ELFT>();
decompressSections();
mergeSections();
if (Config->ICF)
Added: lld/trunk/test/ELF/as-needed-weak.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/as-needed-weak.s?rev=330788&view=auto
==============================================================================
--- lld/trunk/test/ELF/as-needed-weak.s (added)
+++ lld/trunk/test/ELF/as-needed-weak.s Tue Apr 24 17:29:13 2018
@@ -0,0 +1,22 @@
+# REQUIRES: x86
+
+# RUN: echo '.globl foo; .type foo, @function; foo:' | \
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux - -o %t1.o
+# RUN: ld.lld -shared -o %t1.so -soname libfoo %t1.o
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t2.o
+# RUN: ld.lld -o %t.exe %t2.o --as-needed %t1.so
+# RUN: llvm-readelf -dynamic-table -dyn-symbols %t.exe | FileCheck %s
+
+# CHECK-NOT: libfoo
+
+# CHECK: Symbol table of .hash for image:
+# CHECK-NEXT: Num Buc: Value Size Type Bind Vis Ndx Name
+# CHECK-NEXT: 1 1: 0000000000000000 0 FUNC WEAK DEFAULT UND foo@
+
+.globl _start
+.weak foo
+
+_start:
+ mov $foo, %eax
+ callq foo
Modified: lld/trunk/test/ELF/gc-sections-shared.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gc-sections-shared.s?rev=330788&r1=330787&r2=330788&view=diff
==============================================================================
--- lld/trunk/test/ELF/gc-sections-shared.s (original)
+++ lld/trunk/test/ELF/gc-sections-shared.s Tue Apr 24 17:29:13 2018
@@ -25,6 +25,15 @@
# CHECK-NEXT: Section: Undefined (0x0)
# CHECK-NEXT: }
# CHECK-NEXT: Symbol {
+# CHECK-NEXT: Name: qux
+# CHECK-NEXT: Value:
+# CHECK-NEXT: Size:
+# CHECK-NEXT: Binding: Weak
+# CHECK-NEXT: Type:
+# CHECK-NEXT: Other:
+# CHECK-NEXT: Section: Undefined
+# CHECK-NEXT: }
+# CHECK-NEXT: Symbol {
# CHECK-NEXT: Name: bar
# CHECK-NEXT: Value:
# CHECK-NEXT: Size:
@@ -51,15 +60,6 @@
# CHECK-NEXT: Other:
# CHECK-NEXT: Section: .text
# CHECK-NEXT: }
-# CHECK-NEXT: Symbol {
-# CHECK-NEXT: Name: qux
-# CHECK-NEXT: Value:
-# CHECK-NEXT: Size:
-# CHECK-NEXT: Binding: Weak
-# CHECK-NEXT: Type:
-# CHECK-NEXT: Other:
-# CHECK-NEXT: Section: Undefined
-# CHECK-NEXT: }
# CHECK-NEXT: ]
# CHECK-NOT: NEEDED
@@ -68,59 +68,7 @@
# Test with %t.o at the end too.
# RUN: ld.lld --gc-sections --export-dynamic-symbol foo -o %t --as-needed %t2.so %t3.so %t4.so %t.o
-# RUN: llvm-readobj --dynamic-table --dyn-symbols %t | FileCheck --check-prefix=CHECK2 %s
-
-# CHECK2: DynamicSymbols [
-# CHECK2-NEXT: Symbol {
-# CHECK2-NEXT: Name:
-# CHECK2-NEXT: Value:
-# CHECK2-NEXT: Size:
-# CHECK2-NEXT: Binding: Local
-# CHECK2-NEXT: Type:
-# CHECK2-NEXT: Other:
-# CHECK2-NEXT: Section: Undefined (0x0)
-# CHECK2-NEXT: }
-# CHECK2-NEXT: Symbol {
-# CHECK2-NEXT: Name: bar
-# CHECK2-NEXT: Value:
-# CHECK2-NEXT: Size:
-# CHECK2-NEXT: Binding: Global
-# CHECK2-NEXT: Type:
-# CHECK2-NEXT: Other:
-# CHECK2-NEXT: Section: .text
-# CHECK2-NEXT: }
-# CHECK2-NEXT: Symbol {
-# CHECK2-NEXT: Name: baz
-# CHECK2-NEXT: Value:
-# CHECK2-NEXT: Size:
-# CHECK2-NEXT: Binding: Global
-# CHECK2-NEXT: Type:
-# CHECK2-NEXT: Other:
-# CHECK2-NEXT: Section: Undefined
-# CHECK2-NEXT: }
-# CHECK2-NEXT: Symbol {
-# CHECK2-NEXT: Name: qux
-# CHECK2-NEXT: Value:
-# CHECK2-NEXT: Size:
-# CHECK2-NEXT: Binding: Weak
-# CHECK2-NEXT: Type:
-# CHECK2-NEXT: Other:
-# CHECK2-NEXT: Section: Undefined
-# CHECK2-NEXT: }
-# CHECK2-NEXT: Symbol {
-# CHECK2-NEXT: Name: foo
-# CHECK2-NEXT: Value:
-# CHECK2-NEXT: Size:
-# CHECK2-NEXT: Binding: Global
-# CHECK2-NEXT: Type:
-# CHECK2-NEXT: Other:
-# CHECK2-NEXT: Section: .text
-# CHECK2-NEXT: }
-# CHECK2-NEXT: ]
-
-# CHECK2-NOT: NEEDED
-# CHECK2: NEEDED Shared library: [{{.*}}3.so]
-# CHECK2-NOT: NEEDED
+# RUN: llvm-readobj --dynamic-table --dyn-symbols %t | FileCheck --check-prefix=CHECK %s
.section .text.foo, "ax"
.globl foo
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