[Tarantool-patches] [PATCH luajit] Fix C file generation in jit.bcsave.

[Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

From: Sergey Bronnikov <sergeyb@tarantool.org>

Thanks to codicodi.

(cherry picked from commit 62903bacf4abbb1c6df0f395553eeaf1f68352c6)

LuaJIT allows exporting bytecode to a C file using option `-b`, see [1].
For building generated C file in C++ projects C file uses a macro
`__cplusplus` [2], but this macro was broken by commit a9dd47b7fcde
("Extend -b to generate c/h/obj/o files with embedded bytecode."). With
this breakage C/C++ compiler removes definition of array with bytecode
and resulted object file has missed a symbol with bytecode.

The patch fixes broken macro.

Note, test test/lua-Harness-tests/411-luajit.t checks a precense of
macro `__cplusplus` in generated C file, however it doesn't catch the
bug.

Sergey Bronnikov:
* added the description and the test for the problem

Part of tarantool/tarantool#9145

1. https://luajit.org/running.html
2. https://en.cppreference.com/w/cpp/preprocessor/replace
---
PR: https://github.com/tarantool/tarantool/pull/9276
Epic: https://github.com/tarantool/tarantool/issues/9145
Issue: none

 src/jit/bcsave.lua                            |  2 +-
 test/tarantool-tests/CMakeLists.txt           |  1 +
 .../lj-bytecode-c-broken-macro.test.lua       | 13 ++++++++++++
 .../lj-bytecode-c-broken-macro/CMakeLists.txt | 21 +++++++++++++++++++
 .../lj-bytecode-c-broken-macro/lj_lib_xxx.lua |  4 ++++
 5 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 test/tarantool-tests/lj-bytecode-c-broken-macro.test.lua
 create mode 100644 test/tarantool-tests/lj-bytecode-c-broken-macro/CMakeLists.txt
 create mode 100644 test/tarantool-tests/lj-bytecode-c-broken-macro/lj_lib_xxx.lua

diff --git a/src/jit/bcsave.lua b/src/jit/bcsave.lua
index 41081184..5a12c7d0 100644
--- a/src/jit/bcsave.lua
+++ b/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
diff --git a/test/tarantool-tests/CMakeLists.txt b/test/tarantool-tests/CMakeLists.txt
index c15d6037..838e359a 100644
--- a/test/tarantool-tests/CMakeLists.txt
+++ b/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-bytecode-c-broken-macro)
 
 # The part of the memory profiler toolchain is located in tools
 # directory, jit, profiler, and bytecode toolchains are located
diff --git a/test/tarantool-tests/lj-bytecode-c-broken-macro.test.lua b/test/tarantool-tests/lj-bytecode-c-broken-macro.test.lua
new file mode 100644
index 00000000..2047adac
--- /dev/null
+++ b/test/tarantool-tests/lj-bytecode-c-broken-macro.test.lua
@@ -0,0 +1,13 @@
+local tap = require('tap')
+local test = tap.test('lj-jit-bcsave-c-generation')
+
+test:plan(3)
+
+local module_name = 'lj_lib_xxx'
+local ok, module = pcall(require, module_name)
+local message = ('symbol "%s" is available in a library'):format(module_name)
+test:ok(ok == true, message)
+test:is(module.a, 1)
+test:is(module.b, 2)
+
+test:done(true)
diff --git a/test/tarantool-tests/lj-bytecode-c-broken-macro/CMakeLists.txt b/test/tarantool-tests/lj-bytecode-c-broken-macro/CMakeLists.txt
new file mode 100644
index 00000000..aa715067
--- /dev/null
+++ b/test/tarantool-tests/lj-bytecode-c-broken-macro/CMakeLists.txt
@@ -0,0 +1,21 @@
+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}
+  DEPENDS luajit-main ${LUA_FILE}
+  BYPRODUCTS ${C_FILE}
+  COMMENT "Exporting bytecode to a C file"
+  VERBATIM
+)
+
+BuildTestCLib(${LIB_NAME} ${C_FILE})
+add_dependencies(${LIB_NAME} export_bc)
diff --git a/test/tarantool-tests/lj-bytecode-c-broken-macro/lj_lib_xxx.lua b/test/tarantool-tests/lj-bytecode-c-broken-macro/lj_lib_xxx.lua
new file mode 100644
index 00000000..591dfc8b
--- /dev/null
+++ b/test/tarantool-tests/lj-bytecode-c-broken-macro/lj_lib_xxx.lua
@@ -0,0 +1,4 @@
+return {
+  a = 1,
+  b = 2,
+}
-- 
2.34.1