[lld] 6e72c62 - [ELF] Remove duplicate SHT_CREL writeTo branch and cover discarded section symbol path. NFC (#195558)

[via llvm-commits]

Author: Fangrui Song
Date: 2026-05-03T16:11:07-07:00
New Revision: 6e72c62229bedbf5d6f09098b5a42945553650d7

URL: https://github.com/llvm/llvm-project/commit/6e72c62229bedbf5d6f09098b5a42945553650d7
DIFF: https://github.com/llvm/llvm-project/commit/6e72c62229bedbf5d6f09098b5a42945553650d7.diff

LOG: [ELF] Remove duplicate SHT_CREL writeTo branch and cover discarded section symbol path. NFC (#195558)

OutputSection::writeTo had two identical
`if (type == SHT_CREL && !(flags & SHF_ALLOC))` blocks added together in
0af07c078798 (#98115). Drop a dead copy.

A section relocation against a /DISCARD/'d section sees the section
symbol demoted to Undefined. Add a -r --crel case to relocatable-crel.s
that exercises that path.

Added: 
    

Modified: 
    lld/ELF/OutputSections.cpp
    lld/test/ELF/relocatable-crel.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 278e9f56b1d11..ce5f1e551078d 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -536,12 +536,6 @@ void OutputSection::writeTo(Ctx &ctx, uint8_t *buf, parallel::TaskGroup &tg) {
   if (nonZeroFiller)
     fill(buf, sections.empty() ? size : sections[0]->outSecOff, filler);
 
-  if (type == SHT_CREL && !(flags & SHF_ALLOC)) {
-    buf += encodeULEB128(crelHeader, buf);
-    memcpy(buf, crelBody.data(), crelBody.size());
-    return;
-  }
-
   auto fn = [=, &ctx](size_t begin, size_t end) {
     size_t numSections = sections.size();
     for (size_t i = begin; i != end; ++i) {

diff  --git a/lld/test/ELF/relocatable-crel.s b/lld/test/ELF/relocatable-crel.s
index 6e97c3e24d66c..28a2f96d979f4 100644
--- a/lld/test/ELF/relocatable-crel.s
+++ b/lld/test/ELF/relocatable-crel.s
@@ -105,3 +105,25 @@ fb:
 .rept 12
 .long _start
 .endr
+
+#--- c.s
+## The section symbol is demoted to Undefined, so encodeOneCrel emits R_*_NONE with symidx=0.
+# RUN: llvm-mc -filetype=obj -triple=x86_64 -crel c.s -o c.o
+# RUN: ld.lld -r -T c.lds c.o -o out3
+# RUN: llvm-readobj -r out3 | FileCheck %s --check-prefix=DISCARD
+
+# DISCARD:      .crel.data {
+# DISCARD-NEXT:   0x0 R_X86_64_32 foo 0x1
+# DISCARD-NEXT:   0x4 R_X86_64_NONE - 0x0
+# DISCARD-NEXT:   0x8 R_X86_64_32 foo 0x2
+# DISCARD-NEXT: }
+.section .text.discard,"ax"
+.byte 0
+
+.data
+.long foo+1
+.long .text.discard
+.long foo+2
+
+#--- c.lds
+SECTIONS { /DISCARD/ : { *(.text.discard) } }