[lld] 6467649 - [ELF] Make --trace-symbol track preempted shared definitions

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-05-19T08:56:35-07:00
New Revision: 64676499741cb985146ab982a67da859ff8f4f4d

URL: https://github.com/llvm/llvm-project/commit/64676499741cb985146ab982a67da859ff8f4f4d
DIFF: https://github.com/llvm/llvm-project/commit/64676499741cb985146ab982a67da859ff8f4f4d.diff

LOG: [ELF] Make --trace-symbol track preempted shared definitions

Note, we still name a preempted SharedSymbol "shared definition",
instead of "reference" as printed by GNU ld. This difference should not matter.

```
// GNU ld
ld.bfd: t: definition of f at v1
ld.bfd: t.so: reference to f at v1
```

Reviewed By: psmith

Differential Revision: https://reviews.llvm.org/D80143

Added: 
    

Modified: 
    lld/ELF/Symbols.cpp
    lld/test/ELF/trace-symbols.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index f1b44069405e..ff1e600fa2d5 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -726,5 +726,6 @@ void Symbol::resolveShared(const SharedSymbol &other) {
     uint8_t bind = binding;
     replace(other);
     binding = bind;
-  }
+  } else if (traced)
+    printTraceSymbol(&other);
 }

diff  --git a/lld/test/ELF/trace-symbols.s b/lld/test/ELF/trace-symbols.s
index b6f8bea79d12..f5211b367eb4 100644
--- a/lld/test/ELF/trace-symbols.s
+++ b/lld/test/ELF/trace-symbols.s
@@ -13,6 +13,11 @@
 # RUN: rm -f %t2.a
 # RUN: llvm-ar rcs %t2.a %t2
 
+# RUN: ld.lld -y foo -shared %t1 %t1.so -o /dev/null | \
+# RUN:   FileCheck --check-prefix=PREEMPT %s --implicit-check-not=foo
+# PREEMPT:      trace-symbols.s.tmp1: definition of foo
+# PREEMPT-NEXT: trace-symbols.s.tmp1.so: shared definition of foo
+
 # RUN: ld.lld -y foo -trace-symbol common -trace-symbol=hsymbol \
 # RUN:   %t %t1 %t2 -o %t3 | FileCheck -check-prefix=OBJECTRFOO %s
 # OBJECTRFOO: trace-symbols.s.tmp: reference to foo