[libc] Minor error on install step after building on LLVM 18

[lucasreis1]

I've been seeing a minor error when building libc using Ninja during the install step pertaining crti.o and crtn.o. Particularly, both files are never compiled and thus cmake returns me an error when installing libc:

CMake Error at projects/libc/startup/linux/cmake_install.cmake:55 (file):
  file INSTALL cannot find
  "/home/lucas.reis/llvm-18/build/projects/libc/startup/linux/CMakeFiles/libc.startup.linux.crti.dir/./crti.cpp.o":
  No such file or directory.
Call Stack (most recent call first):
  projects/libc/startup/cmake_install.cmake:47 (include)
  projects/libc/cmake_install.cmake:77 (include)
  projects/cmake_install.cmake:47 (include)
  cmake_install.cmake:122 (include)


FAILED: CMakeFiles/install.util 

If I manually compile the object by calling ninja, the install works accordingly after:

lucas.reis:~/llvm-18/build$ ninja libc.startup.linux.crti
[1/1] Building CXX object projects/libc/startup/linux/CMakeFiles/libc.startup.linux.crti.dir/crti.cpp.o
lucas.reis:~/llvm-18/build$ ninja libc.startup.linux.crtn
[1/1] Building CXX object projects/libc/startup/linux/CMakeFiles/libc.startup.linux.crtn.dir/crtn.cpp.o

It is my understanding that those files are built with EXCLUDE_FROM_ALL:

llvm-project/libc/cmake/modules/LLVMLibCObjectRules.cmake

Lines 383 to 389 in 1118c2e

	add_library(
	${fq_target_name}
	EXCLUDE_FROM_ALL
	OBJECT
	${ADD_OBJECT_SRCS}
	${ADD_OBJECT_HDRS}
	)

and thus not compiled excplicitly unless requested, but they are still required in the install step:

llvm-project/libc/startup/linux/CMakeLists.txt

Lines 116 to 137 in 1118c2e

	add_startup_object(
	crti
	SRC
	crti.cpp
	)
	add_startup_object(
	crtn
	SRC
	crtn.cpp
	)
	add_custom_target(libc-startup)
	set(startup_components crt1 crti crtn)
	foreach(target IN LISTS startup_components)
	set(fq_target_name libc.startup.linux.${target})
	add_dependencies(libc-startup ${fq_target_name})
	install(FILES $<TARGET_OBJECTS:${fq_target_name}>
	DESTINATION ${CMAKE_INSTALL_LIBDIR}
	RENAME $<TARGET_PROPERTY:${fq_target_name},OUTPUT_NAME>
	COMPONENT libc)
	endforeach()

Being startup object files it makes sense to me that they should be dependencies for libc to build on linux.

[michaelrj-google]

I think this has been solved. Closing as fixed.