From cb248f8c2a79fbddfdfed0039390e49512410a80 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin@martin.st>
Date: Mon, 24 Jun 2024 20:02:39 +0300
Subject: [LLD] [COFF] Don't crash on an empty -entry: argument (#96058)

We can't pass an empty string to addUndefined().

This fixes the crash that was encountered in
https://github.com/llvm/llvm-project/issues/93309 (turning the crash
into a properly handled error; making it do the right thing is handled
in https://github.com/llvm/llvm-project/pull/96055).
---
 lld/COFF/Driver.cpp           |  4 ++++
 lld/test/COFF/invalid-entry.s | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 lld/test/COFF/invalid-entry.s

diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 1755017..cef6271 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -413,6 +413,8 @@ void LinkerDriver::parseDirectives(InputFile *file) {
         enqueuePath(*path, false, false);
       break;
     case OPT_entry:
+      if (!arg->getValue()[0])
+        fatal("missing entry point symbol name");
       ctx.config.entry = addUndefined(mangle(arg->getValue()));
       break;
     case OPT_failifmismatch:
@@ -2249,6 +2251,8 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
   {
     llvm::TimeTraceScope timeScope("Entry point");
     if (auto *arg = args.getLastArg(OPT_entry)) {
+      if (!arg->getValue()[0])
+        fatal("missing entry point symbol name");
       config->entry = addUndefined(mangle(arg->getValue()));
     } else if (!config->entry && !config->noEntry) {
       if (args.hasArg(OPT_dll)) {
diff --git a/lld/test/COFF/invalid-entry.s b/lld/test/COFF/invalid-entry.s
new file mode 100644
index 0000000..8973dfb
--- /dev/null
+++ b/lld/test/COFF/invalid-entry.s
@@ -0,0 +1,20 @@
+# REQUIRES: x86
+# RUN: split-file %s %t.dir && cd %t.dir
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows test.s -o test.obj
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows drectve.s -o drectve.obj
+
+# RUN: env LLD_IN_TEST=1 not lld-link -out:out.dll test.obj -dll -entry: 2>&1 | FileCheck %s
+# RUN: env LLD_IN_TEST=1 not lld-link -out:out.dll test.obj -dll drectve.obj 2>&1 | FileCheck %s
+
+# CHECK: error: missing entry point symbol name
+
+#--- test.s
+        .text
+        .globl func
+func:
+        ret
+
+#--- drectve.s
+        .section .drectve, "yn"
+        .ascii " -entry:"
-- 
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