[clang] [clang][Driver] Fix safestack -u ordering (PR #98468)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Rainer Orth (rorth)

<details>
<summary>Changes</summary>

When re-enabling safestack testing on Solaris after the unexplained b0260c5b1052f8e3ff1ec77dc42a11f42da762cc, all tests `FAIL`ed to link:

```
Undefined			first referenced
 symbol  			    in file
__safestack_unsafe_stack_ptr        buffer-copy-vla.o
__safestack_init                    (command line)
ld: fatal: symbol referencing errors
```

The problem is that `-u __safestack_init` was passed to the linker after the corresponding version of `libclang_rt.safestack-*.a`.  Since the Solaris linker (like Unix linkers for decades) respects the command line argument order (unlike e.g. GNU ld which uses GNU getopt), this cannot work.  Fixed by moving the `-u` arg further to the front.  Two affected testcases were fixed accordingly.

Tested on `amd64-pc-solaris2.11`, `sparcv9-sun-solaris2.11`, `x86_64-pc-linux-gnu`, and `sparc64-unknown-linux-gnu`.

---
Full diff: https://github.com/llvm/llvm-project/pull/98468.diff


3 Files Affected:

- (modified) clang/lib/Driver/ToolChains/CommonArgs.cpp (+6-4) 
- (modified) clang/test/Driver/ohos.c (+1-1) 
- (modified) clang/test/Driver/sanitizer-ld.c (+1-1) 


``````````diff
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 80a2b2bf31183..019df16a909f4 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -1534,6 +1534,12 @@ bool tools::addSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
                              RequiredSymbols);
   }
 
+  // -u options must be added before the runtime libs that resolve them.
+  for (auto S : RequiredSymbols) {
+    CmdArgs.push_back("-u");
+    CmdArgs.push_back(Args.MakeArgString(S));
+  }
+
   // Inject libfuzzer dependencies.
   if (SanArgs.needsFuzzer() && SanArgs.linkRuntimes() &&
       !Args.hasArg(options::OPT_shared)) {
@@ -1566,10 +1572,6 @@ bool tools::addSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
     addSanitizerRuntime(TC, Args, CmdArgs, RT, false, false);
     AddExportDynamic |= !addSanitizerDynamicList(TC, Args, CmdArgs, RT);
   }
-  for (auto S : RequiredSymbols) {
-    CmdArgs.push_back("-u");
-    CmdArgs.push_back(Args.MakeArgString(S));
-  }
   // If there is a static runtime with no dynamic list, force all the symbols
   // to be dynamic to be sure we export sanitizer interface functions.
   if (AddExportDynamic)
diff --git a/clang/test/Driver/ohos.c b/clang/test/Driver/ohos.c
index b1ce61e7227b6..8de4e6de57f7f 100644
--- a/clang/test/Driver/ohos.c
+++ b/clang/test/Driver/ohos.c
@@ -95,8 +95,8 @@
 // RUN:     | FileCheck %s -check-prefix=CHECK-SAFESTACK
 // CHECK-SAFESTACK: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // CHECK-SAFESTACK: "-fsanitize=safe-stack"
-// CHECK-SAFESTACK: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}arm-liteos-ohos{{/|\\\\}}libclang_rt.safestack.a"
 // CHECK-SAFESTACK: "__safestack_init"
+// CHECK-SAFESTACK: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}arm-liteos-ohos{{/|\\\\}}libclang_rt.safestack.a"
 
 // RUN: %clang %s -### --target=arm-liteos \
 // RUN:     -fsanitize=address 2>&1 \
diff --git a/clang/test/Driver/sanitizer-ld.c b/clang/test/Driver/sanitizer-ld.c
index 48e4ea1f7dcb5..c83066a334001 100644
--- a/clang/test/Driver/sanitizer-ld.c
+++ b/clang/test/Driver/sanitizer-ld.c
@@ -753,8 +753,8 @@
 // CHECK-SAFESTACK-LINUX: "{{(.*[^-.0-9A-Z_a-z])?}}ld{{(.exe)?}}"
 // CHECK-SAFESTACK-LINUX-NOT: "-lc"
 // CHECK-SAFESTACK-LINUX-NOT: whole-archive
-// CHECK-SAFESTACK-LINUX: libclang_rt.safestack.a"
 // CHECK-SAFESTACK-LINUX: "-u" "__safestack_init"
+// CHECK-SAFESTACK-LINUX: libclang_rt.safestack.a"
 // CHECK-SAFESTACK-LINUX: "-lpthread"
 // CHECK-SAFESTACK-LINUX: "-ldl"
 // CHECK-SAFESTACK-LINUX: "-lresolv"

``````````

</details>


https://github.com/llvm/llvm-project/pull/98468