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[libc] warn when depending on public entrypoints #146163

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[libc] warn when depending on public entrypoints #146163

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7f6ca21
[libc] warn when depending on public entrypoints
michaelrj-google Jun 27, 2025
4688e12
address comments
michaelrj-google Jul 2, 2025
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58 changes: 54 additions & 4 deletions libc/cmake/modules/LLVMLibCObjectRules.cmake
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Original file line number Diff line number Diff line change
@@ -1,4 +1,33 @@
set(OBJECT_LIBRARY_TARGET_TYPE "OBJECT_LIBRARY")
set(ENTRYPOINT_OBJ_TARGET_TYPE "ENTRYPOINT_OBJ")
set(ENTRYPOINT_EXT_TARGET_TYPE "ENTRYPOINT_EXT")

# Rule to check if a list of dependencies contains any entrypoint objects. Returns a list in entrypoint_deps.
function(check_entrypoint_deps entrypoint_deps)
set(PUBLIC_DEPS "")
set(fq_deps_list "")
list(APPEND fq_deps_list ${ARGN})

#don't warn for deps that are allowed, such as errno
set(ALLOWED_DEPS
"libc.src.errno.errno"
"libc.src.setjmp.longjmp"
)
list(REMOVE_ITEM fq_deps_list ${ALLOWED_DEPS})

foreach(dep IN LISTS fq_deps_list)
if(NOT TARGET ${dep})
continue()
endif()

get_target_property(target_type ${dep} "TARGET_TYPE")
if(${target_type} STREQUAL ${ENTRYPOINT_OBJ_TARGET_TYPE})
list(APPEND PUBLIC_DEPS ${dep})
endif()
endforeach()
set(${entrypoint_deps} ${PUBLIC_DEPS} PARENT_SCOPE)
endfunction()


# Rule which is essentially a wrapper over add_library to compile a set of
# sources to object files.
Expand Down Expand Up @@ -65,6 +94,18 @@ function(create_object_library fq_target_name)
target_include_directories(${fq_target_name} PRIVATE ${LIBC_SOURCE_DIR})
target_compile_options(${fq_target_name} PRIVATE ${compile_options})

#loop through the deps, check if any have the TARGET_TYPE of ENTRYPOINT_OBJ_TARGET_TYPE, and print a warning if they do.
if(LIBC_CMAKE_VERBOSE_LOGGING)
set(entrypoint_deps "")
if(NOT "${fq_deps_list}" STREQUAL "")
check_entrypoint_deps(entrypoint_deps ${fq_deps_list})
endif()
if(NOT "${entrypoint_deps}" STREQUAL "")
message(WARNING "Object ${fq_target_name} depends on public entrypoint(s) ${entrypoint_deps}.
Depending on public entrypoints is not allowed in internal code.")
endif()
endif()

if(SHOW_INTERMEDIATE_OBJECTS)
message(STATUS "Adding object library ${fq_target_name}")
if(${SHOW_INTERMEDIATE_OBJECTS} STREQUAL "DEPS")
Expand Down Expand Up @@ -110,7 +151,6 @@ function(add_object_library target_name)
${ARGN})
endfunction(add_object_library)

set(ENTRYPOINT_OBJ_TARGET_TYPE "ENTRYPOINT_OBJ")

# A rule for entrypoint object targets.
# Usage:
Expand Down Expand Up @@ -179,7 +219,6 @@ function(create_entrypoint_object fq_target_name)

get_target_property(obj_type ${fq_dep_name} "TARGET_TYPE")
if((NOT obj_type) OR (NOT ${obj_type} STREQUAL ${ENTRYPOINT_OBJ_TARGET_TYPE}))

message(FATAL_ERROR "The aliasee of an entrypoint alias should be an entrypoint.")
endif()

Expand Down Expand Up @@ -230,6 +269,19 @@ function(create_entrypoint_object fq_target_name)
_get_common_compile_options(common_compile_options "${ADD_ENTRYPOINT_OBJ_FLAGS}")
list(APPEND common_compile_options ${ADD_ENTRYPOINT_OBJ_COMPILE_OPTIONS})
get_fq_deps_list(fq_deps_list ${ADD_ENTRYPOINT_OBJ_DEPENDS})

#loop through the deps, check if any have the TARGET_TYPE of entrypoint_target_type, and print a warning if they do.
if(LIBC_CMAKE_VERBOSE_LOGGING)
set(entrypoint_deps "")
if(NOT "${fq_deps_list}" STREQUAL "")
check_entrypoint_deps(entrypoint_deps ${fq_deps_list})
endif()
if(NOT "${entrypoint_deps}" STREQUAL "")
message(WARNING "Entrypoint ${fq_target_name} depends on public entrypoint(s) ${entrypoint_deps}.
Depending on public entrypoints is not allowed in internal code.")
endif()
endif()

set(full_deps_list ${fq_deps_list} libc.src.__support.common)

if(SHOW_INTERMEDIATE_OBJECTS)
Expand Down Expand Up @@ -390,8 +442,6 @@ function(add_entrypoint_object target_name)
)
endfunction(add_entrypoint_object)

set(ENTRYPOINT_EXT_TARGET_TYPE "ENTRYPOINT_EXT")

# A rule for external entrypoint targets.
# Usage:
# add_entrypoint_external(
Expand Down
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