[lld] [lld][ELF] Suppress `--orphan-handling=error/warn` without `SECTIONS` (PR #93630)

[Igor Kudrin via llvm-commits]

https://github.com/igorkudrin created https://github.com/llvm/llvm-project/pull/93630

Without a linker script, `--orphan-handling=error` or `=warn` reports all input sections, including even well-known sections like `.text`, `.bss`, `.dynamic`, or `.symtab`. However, in this case, no sections should be considered orphans because they all are placed with the same default rules. This patch suppresses errors/warnings for placing orphan sections if no linker script with the `SECTIONS` command is provided.

The proposed behavior matches GNU gold. GNU ld in the same scenario only reports sections that are not in its default linker script, thus, it avoids complaining about `.text` and similar.

>From 934b0bffce32c49435ee0829277b7059fbe6aa7c Mon Sep 17 00:00:00 2001
From: Igor Kudrin <ikudrin at accesssoftek.com>
Date: Tue, 28 May 2024 18:42:39 -0700
Subject: [PATCH] [lld][ELF] Suppress `--orphan-handling=error/warn` without
 `SECTIONS`

Without a linker script, `--orphan-handling=error` or `=warn` reports
all input sections, including even well-known sections like `.text`,
`.bss`, `.dynamic`, or `.symtab`. However, in this case, no sections
should be considered orphans because they all are placed with the same
default rules. This patch suppresses errors/warnings for placing orphan
sections if no linker script with the `SECTIONS` command is provided.

The proposed behavior matches GNU gold. GNU ld in the same scenario only
reports sections that are not in its default linker script, thus, it
avoids complaining about `.text` and similar.
---
 lld/ELF/LinkerScript.cpp                  |  3 ++-
 lld/test/ELF/linkerscript/orphan-report.s | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 3ba59c112b8a8..94a39034d629f 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -936,7 +936,8 @@ void LinkerScript::addOrphanSections() {
 
 void LinkerScript::diagnoseOrphanHandling() const {
   llvm::TimeTraceScope timeScope("Diagnose orphan sections");
-  if (config->orphanHandling == OrphanHandlingPolicy::Place)
+  if (config->orphanHandling == OrphanHandlingPolicy::Place ||
+      !hasSectionsCommand)
     return;
   for (const InputSectionBase *sec : orphanSections) {
     // .relro_padding is inserted before DATA_SEGMENT_RELRO_END, if present,
diff --git a/lld/test/ELF/linkerscript/orphan-report.s b/lld/test/ELF/linkerscript/orphan-report.s
index 3dca23267ec64..cc7d8286b6373 100644
--- a/lld/test/ELF/linkerscript/orphan-report.s
+++ b/lld/test/ELF/linkerscript/orphan-report.s
@@ -11,6 +11,17 @@
 # RUN: ld.lld -shared --orphan-handling=place -o %t.out --script %t.script \
 # RUN:   %t.o 2>&1 -verbose  -error-limit=0 | FileCheck %s --check-prefix=DEFAULT
 
+## Check --orphan-handling=error or =warn do not report errors if no linker
+## script is used.
+# RUN: ld.lld -shared -orphan-handling=error -o /dev/null %t.o 2>&1 | \
+# RUN:   FileCheck %s --allow-empty --check-prefix=DEFAULT
+# RUN: ld.lld -shared -orphan-handling=warn -o /dev/null %t.o 2>&1 | \
+# RUN:   FileCheck %s --allow-empty --check-prefix=DEFAULT
+# RUN: ld.lld -r -orphan-handling=error -o /dev/null %t.o 2>&1 | \
+# RUN:   FileCheck %s --allow-empty --check-prefix=DEFAULT
+# RUN: ld.lld -r -orphan-handling=warn -o /dev/null %t.o 2>&1 | \
+# RUN:   FileCheck %s --allow-empty --check-prefix=DEFAULT
+
 ## Check --orphan-handling=error reports errors about orphans.
 # RUN: not ld.lld --orphan-handling=error -o /dev/null -T %t.script \
 # RUN:   %t.o 2>&1 | FileCheck %s --check-prefixes=COMMON,SYMTAB