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build(cmake): silence benign macOS ranlib and ld warnings

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POSIX/SITL builds on macOS produce two classes of benign warnings that
clutter output and obscure real issues:

  ranlib: warning: 'lib*.a(foo.o)' has no symbols
  ld: warning: ignoring duplicate libraries: ...

The ranlib warnings come from sources wrapped in #if defined(CONFIG_*)
guards (i2c.cpp, spi.cpp, board_common.c, pab_manifest.c,
px4_log_history.cpp) and dummy.cpp placeholders, which legitimately
compile to empty object files on POSIX. GNU ranlib ignores this;
Apple's warns. The warning is emitted by 'ar qc' (which implicitly
builds a symbol table), not by ranlib itself, so overriding only
ARCHIVE_FINISH is insufficient. Use 'ar qcS' to skip the implicit
symbol table, then let ranlib -no_warning_for_no_symbols build it
quietly via ARCHIVE_FINISH.

The duplicate-library warnings come from CMake intentionally
re-emitting static libraries on the link line to resolve circular
dependencies between px4_layer, px4_work_queue, px4_daemon and
lockstep_scheduler. GNU ld silently dedupes; Apple's ld-prime
(Xcode 15+) warns. Pass -no_warn_duplicate_libraries to the linker.

Both fixes are Darwin-only and have no effect on Linux CI or NuttX
builds.

Signed-off-by: Ramon Roche <mrpollo@gmail.com>
This commit is contained in:
Ramon Roche 2026-04-08 21:17:17 -07:00
parent 4c8c9a1e0f
commit c9f1d2ab0f
2 changed files with 28 additions and 0 deletions
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22
CMakeLists.txt
View File

@ -229,6 +229,28 @@ endif()
#
project(px4 CXX C ASM)
# Silence Apple ranlib "has no symbols" warnings. Several PX4 sources are
# wrapped in #if defined(CONFIG_*) guards (e.g. platforms/common/i2c.cpp,
# spi.cpp, board_common.c, pab_manifest.c, px4_log_history.cpp) and some
# libraries carry a dummy.cpp placeholder, all of which legitimately produce
# empty object files on POSIX/SITL. GNU ranlib ignores this; Apple's warns.
#
# The warning is actually emitted by `ar qc` (which implicitly builds a symbol
# table), not by the standalone ranlib call. So we use `ar qcS` to skip the
# implicit symbol table, then let CMAKE_*_ARCHIVE_FINISH run ranlib with the
# -no_warning_for_no_symbols flag to add it quietly.
if(APPLE)
set(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> qcS <TARGET> <LINK_FLAGS> <OBJECTS>")
set(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> qcS <TARGET> <LINK_FLAGS> <OBJECTS>")
set(CMAKE_ASM_ARCHIVE_CREATE "<CMAKE_AR> qcS <TARGET> <LINK_FLAGS> <OBJECTS>")
set(CMAKE_C_ARCHIVE_APPEND "<CMAKE_AR> qS <TARGET> <LINK_FLAGS> <OBJECTS>")
set(CMAKE_CXX_ARCHIVE_APPEND "<CMAKE_AR> qS <TARGET> <LINK_FLAGS> <OBJECTS>")
set(CMAKE_ASM_ARCHIVE_APPEND "<CMAKE_AR> qS <TARGET> <LINK_FLAGS> <OBJECTS>")
set(CMAKE_C_ARCHIVE_FINISH "<CMAKE_RANLIB> -no_warning_for_no_symbols -c <TARGET>")
set(CMAKE_CXX_ARCHIVE_FINISH "<CMAKE_RANLIB> -no_warning_for_no_symbols -c <TARGET>")
set(CMAKE_ASM_ARCHIVE_FINISH "<CMAKE_RANLIB> -no_warning_for_no_symbols -c <TARGET>")
endif()
# CMake build type (Debug Release RelWithDebInfo MinSizeRel Coverage)
if(NOT CMAKE_BUILD_TYPE)
if(${PX4_PLATFORM} STREQUAL "nuttx")

6
platforms/posix/cmake/px4_impl_os.cmake
View File

@ -225,6 +225,12 @@ function(px4_os_add_flags)
if(UNIX AND APPLE)
add_definitions(-D__PX4_DARWIN)
# Silence Apple ld warning about duplicate static libs. CMake intentionally
# re-emits them to resolve circular deps (px4_layer, px4_work_queue,
# px4_daemon, lockstep_scheduler). See also CMAKE_*_ARCHIVE_FINISH override
# at the top of the root CMakeLists.txt for the matching ranlib silence.
add_link_options(LINKER:-no_warn_duplicate_libraries)
elseif(CYGWIN)
add_definitions(
-D__PX4_CYGWIN