[ELF] Linkerscript: never add same input section to output section

[evgeny777]

Summary

Sometimes script contains the following:

.foo : {
   a.o(.foo)
   *(.foo)
}

This script must add .foo section from a.o first and all others after that
Without this patch .foo section from a.o will be added twice

[ruiu]

We check for S->OutSec in getInputSections, so it seems that the input section list returned by createInputSectionList can never contain a section with an output section being set. Does this patch make actual difference?

[evgeny777]

Currently you're accumulating sections in createInputSectionList before adding them to output section, remember?

[ruiu]

Ahh, okay. LGTM.

ELF/LinkerScript.cpp

if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base1.get())) {
         continue;
 
       OutputSectionBase<ELFT> *OutSec;
       bool IsNew;
       std::tie(OutSec, IsNew) = Factory.create(Head, Cmd->Name);
       if (IsNew)
         OutputSections->push_back(OutSec);
       for (InputSectionBase<ELFT> *Sec : V)
+        if (!Sec->OutSec)
           OutSec->addSection(Sec);
     }
   }
 
   // Add orphan sections.
   for (const std::unique_ptr<ObjectFile<ELFT>> &F :
        Symtab<ELFT>::X->getObjectFiles()) {
     for (InputSectionBase<ELFT> *S : F->getSections()) {
       if (isDiscarded(S) || S->OutSec)

test/ELF/linkerscript/linkerscript-input-sec-dup.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+
+# RUN: echo "SECTIONS {.foo : { *(.foo) *(.foo) } }" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -section-headers %t1 | FileCheck %s
+# CHECK:      Sections:
+# CHECK-NEXT: Idx Name          Size      Address          Type
+# CHECK-NEXT:   0               00000000 0000000000000000
+# CHECK-NEXT:   1 .foo          00000004 0000000000000120 DATA
+# CHECK-NEXT:   2 .text         00000001 0000000000000124 TEXT DATA
+
+.global _start
+_start:
+ nop
+
+.section .foo,"a"
+ .long 0