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pcre2 / cmake /PCRE2CheckVscript.cmake
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# Similarly to Autoconf's ax_check_vscript.m4, check whether the linker supports
# version scripts (GNU ld) or map files (Sun linker).
# Sets the "have_var" to TRUE or FALSE depending on the detected support; and if
# support is detected then sets "flag_var" to the appropriate flag to pass to
# the linker (namely, --version-script or -M).
function(pcre2_check_vscript have_var flag_var)
set(${have_var} FALSE PARENT_SCOPE)
set(${flag_var} "" PARENT_SCOPE)
if(MSVC)
return()
endif()
set(first_run FALSE)
if(NOT DEFINED HAVE_VSCRIPT_GNU)
set(first_run TRUE)
message(STATUS "Detecting linker version script support")
endif()
include(CheckCSourceCompiles)
include(CMakePushCheckState)
# The BSD file here is a workaround for the fact that check_c_source_compiles
# very unfortunately only supports linking executables
# with an entrypoint (or a static library), and yet the symbol visibility
# requirements for executables are understandably different on some platforms
# as compared to linking a shared library. On FreeBSD, linking fails if you
# use the linker script to hide various global symbols from /usr/lib/crt1.o.
# https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=269370
# Basically, everyone using --version-script is actually going to be creating
# a shared library. It's a frustrating mismatch.
file(WRITE ${PROJECT_BINARY_DIR}/test-map-file.sym "PCRE2_10.00 { global: exposethis; local: *; };")
file(WRITE ${PROJECT_BINARY_DIR}/test-map-file-bsd.sym "PCRE2_10.00 { global: exposethis; environ; __progname; local: *; };")
file(WRITE ${PROJECT_BINARY_DIR}/test-map-file-broken.sym "PCRE2_10.00 { global: exposethis; local: *; }; {")
set(HAVE_VSCRIPT FALSE)
# Using an executable to check for version-script support is rather delicate,
# because linking in an entrypoint (main) adds extra symbols into the mix.
# If CMake ever added a SHARED_LIBRARY option to check_c_source_compiles, we'd
# use it here.
set(
test_source
[=[
int exposethis = 0, hidethis = 0;
int main(void) {
return exposethis + hidethis;
}
]=]
)
cmake_push_check_state(RESET)
set(CMAKE_REQUIRED_QUIET TRUE)
set(CMAKE_REQUIRED_LINK_OPTIONS "-Wl,--version-script,${PROJECT_BINARY_DIR}/test-map-file.sym")
check_c_source_compiles("${test_source}" HAVE_VSCRIPT_GNU)
if(HAVE_VSCRIPT_GNU)
set(VSCRIPT_FLAG --version-script)
set(HAVE_VSCRIPT TRUE)
else()
set(CMAKE_REQUIRED_LINK_OPTIONS "-Wl,--version-script,${PROJECT_BINARY_DIR}/test-map-file-bsd.sym")
check_c_source_compiles("${test_source}" HAVE_VSCRIPT_BSD)
if(HAVE_VSCRIPT_BSD)
set(VSCRIPT_FLAG --version-script)
set(HAVE_VSCRIPT TRUE)
else()
set(CMAKE_REQUIRED_LINK_OPTIONS "-Wl,-M,${PROJECT_BINARY_DIR}/test-map-file.sym")
check_c_source_compiles("${test_source}" HAVE_VSCRIPT_SUN)
if(HAVE_VSCRIPT_SUN)
set(VSCRIPT_FLAG -M)
set(HAVE_VSCRIPT TRUE)
endif()
endif()
endif()
if(HAVE_VSCRIPT)
# Perform the same logic as ax_check_vscript.m4, to test whether the linker
# silently ignores (and overwrites) linker scripts it doesn't understand.
set(CMAKE_REQUIRED_LINK_OPTIONS "-Wl,${VSCRIPT_FLAG},${PROJECT_BINARY_DIR}/test-map-file-broken.sym")
check_c_source_compiles("${test_source}" HAVE_VSCRIPT_BROKEN)
if(HAVE_VSCRIPT_BROKEN)
set(HAVE_VSCRIPT FALSE)
if(first_run)
message(STATUS "Detecting linker version script support - no (linker overwrites unknown scripts)")
endif()
else()
if(first_run)
message(STATUS "Detecting linker version script support - yes (${VSCRIPT_FLAG})")
endif()
endif()
else()
if(first_run)
message(STATUS "Detecting linker version script support - none detected")
endif()
endif()
cmake_pop_check_state()
file(REMOVE ${PROJECT_BINARY_DIR}/test-map-file.sym)
file(REMOVE ${PROJECT_BINARY_DIR}/test-map-file-bsd.sym)
file(REMOVE ${PROJECT_BINARY_DIR}/test-map-file-broken.sym)
if(HAVE_VSCRIPT)
set(${have_var} TRUE PARENT_SCOPE)
set(${flag_var} "${VSCRIPT_FLAG}" PARENT_SCOPE)
endif()
endfunction()