[clang] [Driver] Some adjustments for reloctable linking on OpenBSD (PR #67254)

[Brad Smith via cfe-commits]

https://github.com/brad0 created https://github.com/llvm/llvm-project/pull/67254

The entry point symbol handling matches our GCC link spec.. ```%{!shared:%{!nostdlib:%{!r:%{!e*:-e __start}}}}```


Came up in discussion here https://github.com/llvm/llvm-project/pull/65644

>From 688d4e92e31c1ca4a634c8174022e6843d7784ca Mon Sep 17 00:00:00 2001
From: Brad Smith <brad at comstyle.com>
Date: Sun, 24 Sep 2023 00:20:53 -0400
Subject: [PATCH] [Driver] Some adjustments for reloctable linking on OpenBSD

---
 clang/lib/Driver/ToolChains/OpenBSD.cpp | 8 +++++---
 clang/test/Driver/openbsd.c             | 4 +++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/OpenBSD.cpp b/clang/lib/Driver/ToolChains/OpenBSD.cpp
index 91fe3837b813333..8d88379ef4c10e7 100644
--- a/clang/lib/Driver/ToolChains/OpenBSD.cpp
+++ b/clang/lib/Driver/ToolChains/OpenBSD.cpp
@@ -121,6 +121,7 @@ void openbsd::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   bool Profiling = Args.hasArg(options::OPT_pg);
   bool Pie = Args.hasArg(options::OPT_pie);
   bool Nopie = Args.hasArg(options::OPT_nopie);
+  bool Relocatable = Args.hasArg(options::OPT_r);
 
   // Silence warning for "clang -g foo.o -o foo"
   Args.ClaimAllArgs(options::OPT_g_Group);
@@ -138,7 +139,7 @@ void openbsd::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   else if (Arch == llvm::Triple::mips64el)
     CmdArgs.push_back("-EL");
 
-  if (!Args.hasArg(options::OPT_nostdlib) && !Shared) {
+  if (!Args.hasArg(options::OPT_nostdlib) && !Shared && !Relocatable) {
     CmdArgs.push_back("-e");
     CmdArgs.push_back("__start");
   }
@@ -149,10 +150,11 @@ void openbsd::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   } else {
     if (Args.hasArg(options::OPT_rdynamic))
       CmdArgs.push_back("-export-dynamic");
-    CmdArgs.push_back("-Bdynamic");
+    if (!Relocatable)
+      CmdArgs.push_back("-Bdynamic");
     if (Shared) {
       CmdArgs.push_back("-shared");
-    } else if (!Args.hasArg(options::OPT_r)) {
+    } else if (!Relocatable) {
       CmdArgs.push_back("-dynamic-linker");
       CmdArgs.push_back("/usr/libexec/ld.so");
     }
diff --git a/clang/test/Driver/openbsd.c b/clang/test/Driver/openbsd.c
index 05d290a309c40c0..a8db20200cd473d 100644
--- a/clang/test/Driver/openbsd.c
+++ b/clang/test/Driver/openbsd.c
@@ -36,10 +36,12 @@
 // RUN:   | FileCheck --check-prefix=CHECK-MIPS64-LD %s
 // RUN: %clang --target=mips64el-unknown-openbsd -### %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MIPS64EL-LD %s
-// CHECK-LD-R:     "-r"
+// CHECK-LD-R-NOT: "-e" "__start"
+// CHECK-LD-R-NOT: "-Bdynamic"
 // CHECK-LD-R-NOT: "-dynamic-linker"
 // CHECK-LD-R-NOT: "-l
 // CHECK-LD-R-NOT: crt{{[^./\\]+}}.o
+// CHECK-LD-R:     "-r"
 // CHECK-LD-S: "-cc1" "-triple" "i686-pc-openbsd"
 // CHECK-LD-S: ld{{.*}}" "-e" "__start" "--eh-frame-hdr" "-Bdynamic" "-dynamic-linker" "{{.*}}ld.so" "-o" "a.out" "{{.*}}crt0.o" "{{.*}}crtbegin.o" "-L{{.*}}" "-s" "{{.*}}.o" "-lcompiler_rt" "-lc" "-lcompiler_rt" "{{.*}}crtend.o"
 // CHECK-LD-T: "-cc1" "-triple" "i686-pc-openbsd"