fix(build): fix attempt windows build

error:  "C atomics require C11 or later"

Signed-off-by: irozzo-1A <iacopo@sysdig.com>

Author: irozzo-1A

cmake/modules/CompilerFlags.cmake

@@ -116,6 +116,11 @@ if(NOT MSVC)
 	add_definitions(-D__STDC_FORMAT_MACROS)
 
 else() # MSVC
+	# C sources (e.g. libscap) use C11 atomics (<stdatomic.h>). MSVC needs /std:c11 and
+	# /experimental:c11atomics (see CMAKE_C_STANDARD and CMAKE_C_FLAGS below). Requires VS 2022
+	# 17.5+.
+	set(CMAKE_C_STANDARD 11)
+
 	set(FALCOSECURITY_LIBS_COMMON_FLAGS
 		"-D_CRT_SECURE_NO_WARNINGS -DWIN32 /EHsc /W3 /Zi /std:c++17"
 	)
@@ -129,6 +134,12 @@ else() # MSVC
 
 	set(CMAKE_C_FLAGS "${FALCOSECURITY_LIBS_COMMON_FLAGS}")
 	set(CMAKE_CXX_FLAGS "${FALCOSECURITY_LIBS_COMMON_FLAGS}")
+	# Enable C11 atomics for .c files (libscap uses <stdatomic.h>). Requires VS 2022 17.5+. Use
+	# add_compile_options so the flag propagates to all C targets in subdirectories (e.g.
+	# scap_engine_savefile); CMAKE_C_FLAGS alone is not reliably applied by the Visual Studio
+	# generator to targets created in add_subdirectory().
+	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /experimental:c11atomics")
+	add_compile_options($<$<COMPILE_LANGUAGE:C>:/experimental:c11atomics>)
 
 	set(CMAKE_C_FLAGS_DEBUG "${FALCOSECURITY_LIBS_DEBUG_FLAGS}")
 	set(CMAKE_CXX_FLAGS_DEBUG "${FALCOSECURITY_LIBS_DEBUG_FLAGS}")

userspace/libscap/CMakeLists.txt

@@ -71,6 +71,10 @@ target_include_directories(scap_buffer PUBLIC $<BUILD_INTERFACE:${LIBS_DIR}/user
 
 add_library(scap scap.c scap_api_version.c scap_savefile.c scap_platform_api.c)
 
+if(MSVC)
+	target_compile_options(scap PRIVATE $<$<COMPILE_LANGUAGE:C>:/experimental:c11atomics>)
+endif()
+
 target_include_directories(
 	scap
 	PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>

userspace/libscap/engine/savefile/CMakeLists.txt

@@ -22,3 +22,9 @@ target_link_libraries(
 	scap_engine_savefile PRIVATE scap_engine_noop scap_platform_util scap_savefile_converter
 								 ${ZLIB_LIB} scap_error
 )
+
+if(MSVC)
+	target_compile_options(
+		scap_engine_savefile PRIVATE $<$<COMPILE_LANGUAGE:C>:/experimental:c11atomics>
+	)
+endif()

userspace/libscap/engine/source_plugin/CMakeLists.txt

@@ -16,5 +16,9 @@ add_library(scap_engine_source_plugin source_plugin.c)
 target_link_libraries(
 	scap_engine_source_plugin PRIVATE scap_event_schema scap_engine_noop scap_error
 )
-
+if(MSVC)
+	target_compile_options(
+		scap_engine_source_plugin PRIVATE $<$<COMPILE_LANGUAGE:C>:/experimental:c11atomics>
+	)
+endif()
 set_scap_target_properties(scap_engine_source_plugin)