Fix C file generation in jit.bcsave.

Thanks to codicodi.

(cherry picked from commit 62903ba)

--- l1.txt      2023-10-18 19:21:23.939547944 +0300
+++ l2.txt      2023-10-18 19:21:28.891489600 +0300
@@ -8,12 +8,11 @@
...
-0000000000002000 R luaJIT_BC_lj_lib_xxx
...

src/jit/bcsave.lua

@@ -133,7 +133,7 @@ local function bcsave_c(ctx, output, s)
   local fp = savefile(output, "w")
   if ctx.type == "c" then
     fp:write(format([[
-#ifdef _cplusplus
+#ifdef __cplusplus
 extern "C"
 #endif
 #ifdef _WIN32

test/tarantool-tests/CMakeLists.txt

@@ -68,6 +68,7 @@ add_subdirectory(lj-727-lightuserdata-itern)
 add_subdirectory(lj-802-panic-at-mcode-protfail)
 add_subdirectory(lj-flush-on-trace)
 add_subdirectory(lj-1004-oom-error-frame)
+add_subdirectory(lj-jit-bcsave-c-generation)
 
 # The part of the memory profiler toolchain is located in tools
 # directory, jit, profiler, and bytecode toolchains are located

test/tarantool-tests/lj-jit-bcsave-c-generation.test.lua

@@ -0,0 +1,13 @@
+local tap = require('tap')
+local test = tap.test('lj-jit-bcsave-c-generation')
+
+test:plan(1)
+
+local module_name = 'lj_lib_xxx'
+local ok, _ = pcall(require, module_name)
+local symbol_name = ('luaJIT_BC_%s'):format(module_name)
+local message = ('symbol "%s" is available in a library'):format(module_name)
+
+test:ok(ok == true, message)
+
+test:done(true)

test/tarantool-tests/lj-jit-bcsave-c-generation/CMakeLists.txt

@@ -0,0 +1,46 @@
+set(LIB_NAME "lj_lib_xxx")
+set(LUA_FILE ${CMAKE_CURRENT_SOURCE_DIR}/${LIB_NAME}.lua)
+set(C_FILE ${LIB_NAME}.c)
+set(CXX_FILE ${LIB_NAME}.cc)
+
+make_lua_path(LUA_PATH
+  PATHS
+    ${PROJECT_SOURCE_DIR}/src/?.lua
+    ${PROJECT_SOURCE_DIR}/src/jit/?.lua
+)
+
+add_custom_target(export_bc
+  COMMAND ${CMAKE_COMMAND} -E env LUA_PATH=${LUA_PATH} ${LUAJIT_BINARY} -b ${LUA_FILE} ${C_FILE}
+  # Enforce CMake to using CXX compiler.
+  # COMMAND ${CMAKE_COMMAND} -E rename ${C_FILE} ${CXX_FILE}
+  DEPENDS luajit-main ${LUA_FILE}
+  # BYPRODUCTS ${CXX_FILE}
+  BYPRODUCTS ${C_FILE}
+  COMMENT "Exporting bytecode to a C file"
+  VERBATIM
+)
+
+# add_custom_command(
+#   OUTPUT ${CXX_FILE}
+#   COMMAND ${CMAKE_COMMAND} -E env LUA_PATH=${LUA_PATH} ${LUAJIT_BINARY} -b ${LUA_FILE} ${C_FILE}
+#   # Enforce CMake to using CXX compiler.
+#   COMMAND ${CMAKE_COMMAND} -E rename ${C_FILE} ${CXX_FILE}
+#   DEPENDS luajit-main ${LUA_FILE}
+#   BYPRODUCTS ${CXX_FILE}
+#   COMMENT "Exporting bytecode to a C file"
+#   VERBATIM
+#   WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+# )
+
+# add_library(${LIB_NAME} SHARED OBJECT EXCLUDE_FROM_ALL ${CXX_FILE})
+# add_dependencies(${LIB_NAME} export_bc)
+# # set_target_properties("xxx" PROPERTIES LINKER_LANGUAGE CXX)
+# set_target_properties(${LIB_NAME} PROPERTIES
+#   LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
+#   PREFIX ""
+# )
+# list(APPEND TESTLIBS ${LIB_NAME})
+
+# BuildTestCLib(${LIB_NAME} ${CXX_FILE})
+BuildTestCLib(${LIB_NAME} ${C_FILE})
+add_dependencies(${LIB_NAME} export_bc)

test/tarantool-tests/lj-jit-bcsave-c-generation/lj_lib_xxx.lua

@@ -0,0 +1,7 @@
+local a = 1
+local b = 2
+
+return {
+  a = a,
+  b = b,
+}