[lld] a27a7b9 - [ELF] --warn-backrefs: don't warn if -u/--export-dynamic-symbol

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-04-08T09:33:22-07:00
New Revision: a27a7b98cd19975e6f2c2e24e4abc1c3a213b15e

URL: https://github.com/llvm/llvm-project/commit/a27a7b98cd19975e6f2c2e24e4abc1c3a213b15e
DIFF: https://github.com/llvm/llvm-project/commit/a27a7b98cd19975e6f2c2e24e4abc1c3a213b15e.diff

LOG: [ELF] --warn-backrefs: don't warn if -u/--export-dynamic-symbol

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D77630

Added: 
    

Modified: 
    lld/ELF/Driver.cpp
    lld/test/ELF/warn-backrefs.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index c90ac589d2d1..2aeeb84f5af9 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -1448,6 +1448,10 @@ static void handleUndefined(Symbol *sym) {
   // eliminate it. Mark the symbol as "used" to prevent it.
   sym->isUsedInRegularObj = true;
 
+  // GNU linkers allow -u foo -ldef -lref. We should not treat it as a backward
+  // reference.
+  backwardReferences.erase(sym);
+
   if (sym->isLazy())
     sym->fetch();
 }

diff  --git a/lld/test/ELF/warn-backrefs.s b/lld/test/ELF/warn-backrefs.s
index 3d6bcb933100..5dec458232ee 100644
--- a/lld/test/ELF/warn-backrefs.s
+++ b/lld/test/ELF/warn-backrefs.s
@@ -62,6 +62,12 @@
 ## --warn-backrefs does not warn.
 # RUN: ld.lld --fatal-warnings --warn-backrefs %t2.a %t1.o %t2.so %t2.a -o /dev/null
 
+## In GNU linkers, -u does not make a backward reference.
+# RUN: ld.lld --fatal-warnings --warn-backrefs -u foo %t2.a %t1.o -o /dev/null
+
+## In GNU gold, --export-dynamic-symbol does not make a backward reference.
+# RUN: ld.lld --fatal-warnings --warn-backrefs --export-dynamic-symbol foo %t2.a %t1.o -o /dev/null
+
 .globl _start, foo
 _start:
   call foo