libc: fails to build with `add_custom_target cannot create target "libc" because another target with the same name already exists`

[sylvestre]

Not sure what caused it. Maybe #117220 by @nickdesaulniers

-- Looking for logf128 - found
-- Targeting M68k
-- Targeting Xtensa
-- Targeting AArch64
-- Setting LIBC_NAMESPACE namespace to '__llvm_libc_20_0_0_'
g++: error: unrecognized command-line option '--print-resource-dir'; did you mean '--print-search-dirs'?
g++: fatal error: no input files
compilation terminated.
-- Set COMPILER_RESOURCE_DIR to /usr/lib/gcc/aarch64-linux-gnu/10/ using --print-search-dirs
-- Building libc for aarch64 on linux with
        LIBC_COMPILE_OPTIONS_DEFAULT: 
-- LIBC_CONF_ENABLE_STRONG_STACK_PROTECTOR: ON

Regression range 356df2d..1e7171f
Fails log:
https://llvm-jenkins.debian.net/job/llvm-toolchain-bullseye-binaries/architecture=arm64,distribution=bullseye,label=arm64/1608/console

[llvmbot]

@llvm/issue-subscribers-libc

Author: Sylvestre Ledru (sylvestre)

Not sure what caused it. Maybe #117220 by @nickdesaulniers ``` -- Looking for logf128 - found -- Targeting M68k -- Targeting Xtensa -- Targeting AArch64 -- Setting LIBC_NAMESPACE namespace to '__llvm_libc_20_0_0_' g++: error: unrecognized command-line option '--print-resource-dir'; did you mean '--print-search-dirs'? g++: fatal error: no input files compilation terminated. -- Set COMPILER_RESOURCE_DIR to /usr/lib/gcc/aarch64-linux-gnu/10/ using --print-search-dirs -- Building libc for aarch64 on linux with LIBC_COMPILE_OPTIONS_DEFAULT: -- LIBC_CONF_ENABLE_STRONG_STACK_PROTECTOR: ON ```

Regression range 356df2d..1e7171f
Fails log:
https://llvm-jenkins.debian.net/job/llvm-toolchain-bullseye-binaries/architecture=arm64,distribution=bullseye,label=arm64/1608/console

[nickdesaulniers]

g++: error: unrecognized command-line option '--print-resource-dir'; did you mean '--print-search-dirs'?
g++: fatal error: no input files

I think is a red herring; I observe that when building llvm-libc with g++; it's orthogonal to #117220 and I don't think that's why your build is failing. I'm looking closer at the logs now to better understand why your build did fail.

[nickdesaulniers]

actual cmake error

CMake Error at cmake/modules/LLVMExternalProjectUtils.cmake:453 (add_custom_target):
  add_custom_target cannot create target "libc" because another target with
  the same name already exists.  The existing target is a static library
  created in source directory "/build/source/libc/lib".  See documentation
  for policy CMP0002 for more details.
Call Stack (most recent call first):
  runtimes/CMakeLists.txt:266 (llvm_ExternalProject_Add)
  runtimes/CMakeLists.txt:559 (runtime_default_target)


CMake Error at cmake/modules/LLVMExternalProjectUtils.cmake:453 (add_custom_target):
  add_custom_target cannot create target "install-libc" because another
  target with the same name already exists.  The existing target is a custom
  target created in source directory "/build/source/libc/lib".  See
  documentation for policy CMP0002 for more details.
Call Stack (most recent call first):
  runtimes/CMakeLists.txt:266 (llvm_ExternalProject_Add)
  runtimes/CMakeLists.txt:559 (runtime_default_target)


CMake Error at cmake/modules/LLVMExternalProjectUtils.cmake:453 (add_custom_target):
  add_custom_target cannot create target "install-libc-stripped" because
  another target with the same name already exists.  The existing target is a
  custom target created in source directory "/build/source/libc/lib".  See
  documentation for policy CMP0002 for more details.
Call Stack (most recent call first):
  runtimes/CMakeLists.txt:266 (llvm_ExternalProject_Add)
  runtimes/CMakeLists.txt:559 (runtime_default_target)


CMake Error at cmake/modules/LLVMExternalProjectUtils.cmake:453 (add_custom_target):
  add_custom_target cannot create target "check-libc" because another target
  with the same name already exists.  The existing target is a custom target
  created in source directory "/build/source/libc/test".  See documentation
  for policy CMP0002 for more details.
Call Stack (most recent call first):
  runtimes/CMakeLists.txt:266 (llvm_ExternalProject_Add)
  runtimes/CMakeLists.txt:559 (runtime_default_target)

[nickdesaulniers]

Do you have the ability to reset the CMakeCache.txt file on this buildbot?

[sylvestre]

as it is built in a new chroot, i don't think we have an existing cache before

[nickdesaulniers]

I wonder if -DLLVM_LIBC_GPU_BUILD=ON is somehow tickling this. @jhuber6 mentioned in #libc on discord:

Trying to fix this but I have no clue why it's broken, keeps telling me that the libc target is already defined

I wonder if it was the same error encountered?

[jhuber6]

It's possible, I did get something similar but I thought i fixed it. I'll do a git pull and clean build and report back.

[jhuber6]

Yep, seems busted on the GPU. I got it working earlier but I guess that was a fluke.

[jhuber6]

Seems to work if you just delete the entirety of the LIBC_NEED_GPU_UTILS check and just make it return if it's a projects build, so likely the logic isn't firing correctly there and returning if we're only trying to build the loader.

[nickdesaulniers]

Seems to work if you just delete the entirety of the LIBC_NEED_GPU_UTILS check and just make it return if it's a projects build

s/LIBC_NEED_GPU_UTILS/LIBC_NEED_LOADER_UTILS/ ?

So:

diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index fd82359022cf..b3607a0f1ea8 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -64,6 +64,9 @@ if(LIBC_BUILD_GPU_LOADER OR NOT LLVM_RUNTIMES_BUILD)
      "${LIBC_TARGET_TRIPLE}" STREQUAL "nvptx64-nvidia-cuda")
     set(LIBC_NEED_LOADER_UTILS TRUE)
   endif()
+  if (NOT LLVM_RUNTIMES_BUILD)
+    return()
+  endif()
   if(LIBC_NEED_LOADER_UTILS)
     add_subdirectory(utils/gpu)
     return()

?

[jhuber6]

There's already a check for that, a solution would be to deprecate the projects build and just make it return unconditionally (after building the utils). But we still kind of support that right now.