[llvm] [llvm-libgcc] Fix symlink path for libcc when LLVM_ENABLE_PER_TARGET_… (PR #165487)

[Khem Raj via llvm-commits]

https://github.com/kraj created https://github.com/llvm/llvm-project/pull/165487

…RUNTIME_DIR is unset

current logic fails when LLVM_ENABLE_PER_TARGET_RUNTIME_DIR = OFF and it ends up with symlinks e.g.

libgcc.a -> ..//usr/lib/clang/21.1.4/lib/linux/libclang_rt.builtins.a

the real library is at
../lib/clang/21.1.4/lib/linux/libclang_rt.builtins-aarch64.a

The relative path is incorrect and its missing to add -arch suffix as well.

So we make checks a bit more explicit to cover this case.

The symlink for libgcc_so.1.0 is made to point to libunwind.so which is functionally correct but it fails some linux distro packaging complain because libunwind.so is made part of -dev package but libgcc_so.1.0 ends up in the real package, and creates an unneeded package -> dev dependency

create the symlink to point to libunwind.so.1 instead then the boundaries of packaging are not crossed and all is well.

>From 4204fd1b62de30418433139fea1b7dad4fff9c59 Mon Sep 17 00:00:00 2001
From: Khem Raj <raj.khem at gmail.com>
Date: Tue, 28 Oct 2025 15:44:49 -0700
Subject: [PATCH] [llvm-libgcc] Fix symlink path for libcc when
 LLVM_ENABLE_PER_TARGET_RUNTIME_DIR is unset

current logic fails when LLVM_ENABLE_PER_TARGET_RUNTIME_DIR = OFF
and it ends up with symlinks e.g.

libgcc.a -> ..//usr/lib/clang/21.1.4/lib/linux/libclang_rt.builtins.a

the real library is at
../lib/clang/21.1.4/lib/linux/libclang_rt.builtins-aarch64.a

The relative path is incorrect and its missing to add -arch suffix
as well.

So we make checks a bit more explicit to cover this case.

The symlink for libgcc_so.1.0 is made to point to libunwind.so
which is functionally correct but it fails some linux distro packaging
complain because libunwind.so is made part of -dev package but
libgcc_so.1.0 ends up in the real package, and creates an unneeded
package -> dev dependency

create the symlink to point to libunwind.so.1 instead then the boundaries
of packaging are not crossed and all is well.

Signed-off-by: Khem Raj <raj.khem at gmail.com>
---
 llvm-libgcc/CMakeLists.txt | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/llvm-libgcc/CMakeLists.txt b/llvm-libgcc/CMakeLists.txt
index 47208fc198692..54009c1104c32 100644
--- a/llvm-libgcc/CMakeLists.txt
+++ b/llvm-libgcc/CMakeLists.txt
@@ -124,11 +124,21 @@ target_link_libraries(unwind_shared PUBLIC
 #===============================================================================
 
 get_compiler_rt_install_dir(${COMPILER_RT_DEFAULT_TARGET_ARCH} install_dir_builtins)
+
+# Drop a leading "lib/" if present so we don't duplicate lib/lib
 string(REGEX REPLACE "^lib/" "" install_dir_builtins "${install_dir_builtins}")
-string(FIND "${install_dir_builtins}" "clang" install_path_contains_triple)
-if(install_path_contains_triple EQUAL -1)
+
+# Decide based on the actual CMake option, not on guessing from the path.
+if (NOT LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)
+  # Flat-ish layout, e.g. usr/lib/clang/21.1.4/lib/linux/
+  # Libraries are named libclang_rt.builtins-<arch>.a
   set(builtins_suffix "-${COMPILER_RT_DEFAULT_TARGET_ARCH}")
+  # Do NOT prepend "../"
 else()
+  # Per-target layout, e.g.
+  # usr/lib/clang/21.1.4/lib/aarch64-unknown-linux-gnu/
+  # Libraries are just libclang_rt.builtins.a
+  set(builtins_suffix "")
   string(PREPEND install_dir_builtins "../")
 endif()
 set(LLVM_LIBGCC_COMPILER_RT ${install_dir_builtins}/libclang_rt.builtins${builtins_suffix}.a)
@@ -137,7 +147,7 @@ add_custom_target(llvm-libgcc ALL
   DEPENDS unwind_shared unwind_static clang_rt.builtins-${COMPILER_RT_DEFAULT_TARGET_ARCH}
   COMMAND ${CMAKE_COMMAND} -E create_symlink ${LLVM_LIBGCC_COMPILER_RT} libgcc.a
   COMMAND ${CMAKE_COMMAND} -E create_symlink libunwind.a libgcc_eh.a
-  COMMAND ${CMAKE_COMMAND} -E create_symlink libunwind.so libgcc_s.so.1.0
+  COMMAND ${CMAKE_COMMAND} -E create_symlink libunwind.so.1 libgcc_s.so.1.0
   COMMAND ${CMAKE_COMMAND} -E create_symlink libgcc_s.so.1.0 libgcc_s.so.1
   COMMAND ${CMAKE_COMMAND} -E create_symlink libgcc_s.so.1 libgcc_s.so
 )