[Driver] Add linker options to support statical linking to shared flang-rt on AIX.

[DanielCChen]

This is to support statical linking to shared flang-rt on AIX.
Users should be able to do flang -static t.f. The a.out generated should not have dependencies on the shared libraries.

[llvmbot]

@llvm/pr-subscribers-clang-driver
@llvm/pr-subscribers-clang

@llvm/pr-subscribers-backend-powerpc

Author: Daniel Chen (DanielCChen)

Changes

This is to support statical linking to shared flang-rt on AIX.
Users should be able to do flang -static t.f. The a.out generated should not have dependencies on the shared libraries.

---

Full diff: https://github.com/llvm/llvm-project/pull/131822.diff

1 Files Affected:

• (modified) clang/lib/Driver/ToolChains/AIX.cpp (+8-1)

diff --git a/clang/lib/Driver/ToolChains/AIX.cpp b/clang/lib/Driver/ToolChains/AIX.cpp
index 001f3a5178943..7ed26c42c80ce 100644
--- a/clang/lib/Driver/ToolChains/AIX.cpp
+++ b/clang/lib/Driver/ToolChains/AIX.cpp
@@ -127,8 +127,15 @@ void aix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   // Force static linking when "-static" is present.
-  if (Args.hasArg(options::OPT_static))
+  if (Args.hasArg(options::OPT_static)) {
     CmdArgs.push_back("-bnso");
+    // The folllowing linker options are needed to statically link to the
+    // shared libflang_rt.runtime.a on AIX
+    CmdArgs.push_back("-bI:/usr/lib/syscalls.exp");
+    CmdArgs.push_back("-bI:/usr/lib/aio.exp");
+    CmdArgs.push_back("-bI:/usr/lib/threads.exp");
+    CmdArgs.push_back("-lcrypt");
+  }
 
   // Add options for shared libraries.
   if (Args.hasArg(options::OPT_shared)) {

[MaskRay]

This change needs a test somewhere at flang/test/Driver/

[DanielCChen]

Thanks for the comment!
Yes. I will add test.

[hubert-reinterpretcast]

Does this add extra options even when libflang_rt.runtime.a is not being linked in?
See https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/ToolChains/AIX.cpp#L359-L365

[DanielCChen]

These extra options will be linked in when flang is the invocation driver and -static is specified. As the driver code is written in PR #131041, libflang_rt.runtime.a is always linked in with the full path name no matter if it is static or shared.

[hubert-reinterpretcast]

As the driver code is written in PR #131041, libflang_rt.runtime.a is always linked in with the full path name no matter if it is static or shared.

The other PR does not change the lines I referenced in a way that causes libflang_rt.runtime.a to always be linked in.

[DanielCChen]

Note that the reason aio.exp is not needed is because flang-rt currently doesn't do asynchronous I/O. Once it is enabled using POSIX aio_* system calls, it will need to export those calls.

[hubert-reinterpretcast]

Note that the reason aio.exp is not needed is because flang-rt currently doesn't do asynchronous I/O. Once it is enabled using POSIX aio_* system calls, it will need to export those calls.

There is also a /usr/lib/posix_aio.exp.

[daltenty]

I think this is a bit misplaced, IIUC these options are needed to link libc statically, not flang_rt itself (-static just happens to mean we link both).

Thus, I think this belongs where we push_back -lc for the AIX toolchain, so here:
https://github.com/llvm/llvm-project/blob/28907a624a8d9561badc20d77254791918ba6210/clang/lib/Driver/ToolChains/AIX.cpp#L357

Also, I don't think this really belongs under the -static option, that is really an ld option which says, only link to static libs. Typically there are separate options to link particular runtimes statically. Since this is really for libc, I'd suggest -static-libc.

[DanielCChen]

After further internal discussion. we decided to withdraw this PR until we hash out a few more details.
Thanks everyone for the comments.