[PATCH] D48771: [ELF] Don't create empty output section for unreferenced PROVIDE symbol

[James Henderson via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL336184: [ELF] Don't create empty output section for unreferenced PROVIDEs (authored by jhenderson, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D48771?vs=153486&id=153880#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D48771

Files:
  lld/trunk/ELF/LinkerScript.cpp
  lld/trunk/test/ELF/linkerscript/provide-empty-section.s


Index: lld/trunk/ELF/LinkerScript.cpp
===================================================================
--- lld/trunk/ELF/LinkerScript.cpp
+++ lld/trunk/ELF/LinkerScript.cpp
@@ -834,9 +834,16 @@
   if (Sec.ExpressionsUseSymbols)
     return false;
 
-  for (BaseCommand *Base : Sec.SectionCommands)
+  for (BaseCommand *Base : Sec.SectionCommands) {
+    if (auto Cmd = dyn_cast<SymbolAssignment>(Base))
+      // Don't create empty output sections just for unreferenced PROVIDE
+      // symbols.
+      if (Cmd->Name != "." && !Cmd->Sym)
+        continue;
+
     if (!isa<InputSectionDescription>(*Base))
       return false;
+  }
   return true;
 }
 
Index: lld/trunk/test/ELF/linkerscript/provide-empty-section.s
===================================================================
--- lld/trunk/test/ELF/linkerscript/provide-empty-section.s
+++ lld/trunk/test/ELF/linkerscript/provide-empty-section.s
@@ -0,0 +1,30 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %tundefined.o
+# RUN: echo "foo=42" | llvm-mc -filetype=obj -triple=x86_64-unknown-linux - -o %tdefined.o
+# RUN: echo "call foo" | llvm-mc -filetype=obj -triple=x86_64-unknown-linux - -o %treference.o
+
+# RUN: echo "SECTIONS { .bar : { PROVIDE(foo = .); } }" > %t.script
+
+# Case 1: Provided symbol is undefined and not referenced - empty section should be removed.
+# RUN: ld.lld %tundefined.o -T %t.script -o %t1.elf
+# RUN: llvm-readobj -sections %t1.elf | FileCheck %s --check-prefix=NOSECTION
+
+# Case 2: Provided symbol is undefined and referenced - empty section should not be removed.
+# RUN: ld.lld %tundefined.o %treference.o -T %t.script -o %t2.elf
+# RUN: llvm-readobj -sections %t2.elf | FileCheck %s --check-prefix=SECTION
+
+# Case 3: Provided symbol is defined and not referenced - empty section should be removed.
+# RUN: ld.lld %tdefined.o -T %t.script -o %t3.elf
+# RUN: llvm-readobj -sections %t3.elf | FileCheck %s --check-prefix=NOSECTION
+
+# Case 4: Provided symbol is defined and referenced - empty section should not be removed.
+# RUN: ld.lld %tdefined.o %treference.o -T %t.script -o %t4.elf
+# RUN: llvm-readobj -sections %t4.elf | FileCheck %s --check-prefix=SECTION
+
+.global _start
+_start:
+    ret
+
+# SECTION: .bar
+# NOSECTION-NOT: .bar


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D48771.153880.patch
Type: text/x-patch
Size: 2288 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180703/d471b81f/attachment.bin>