feat(lua): make sure require'bit' always works, even with PUC lua 5.1

9 files changed, 241 insertions, 4 deletions

diff --git a/MAINTAIN.md b/MAINTAIN.md
index 629327a67a..91f09ee67e 100644
--- a/MAINTAIN.md
+++ b/MAINTAIN.md
@@ -93,6 +93,7 @@ These dependencies are "vendored" (inlined), we must update the sources manually
 * `runtime/lua/vim/inspect.lua`: [inspect.lua](https://github.com/kikito/inspect.lua)
 * `src/nvim/tui/terminfo_defs.h`: terminfo definitions
     * Run `scripts/update_terminfo.sh` to update these definitions.
+* `src/bit.c`: only for PUC lua: port of `require'bit'` from luajit https://bitop.luajit.org/
 * [treesitter parsers](https://github.com/neovim/neovim/blob/fcc24e43e0b5f9d801a01ff2b8f78ce8c16dd551/cmake.deps/CMakeLists.txt#L197-L210)
 
 ### Forks
diff --git a/cmake.deps/cmake/BuildLuarocks.cmake b/cmake.deps/cmake/BuildLuarocks.cmake
index f87d5829b2..cd5aa1ed34 100644
--- a/cmake.deps/cmake/BuildLuarocks.cmake
+++ b/cmake.deps/cmake/BuildLuarocks.cmake
@@ -147,7 +147,7 @@ if(USE_BUNDLED_BUSTED)
     DEPENDS busted)
   add_custom_target(luacheck ALL DEPENDS ${LUACHECK_EXE})
 
-  if (NOT USE_BUNDLED_LUAJIT)
+  if (USE_BUNDLED_LUA OR NOT USE_BUNDLED_LUAJIT)
     # coxpcall
     add_custom_command(OUTPUT ${ROCKS_DIR}/coxpcall
       COMMAND ${LUAROCKS_BINARY} build coxpcall 1.16.0-1 ${LUAROCKS_BUILDARGS}
diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index 32e89bd237..8ae1c6dc40 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -33,6 +33,22 @@ Lua 5.1, not worry about forward-compatibility with future Lua versions.  If
 Nvim ever ships with Lua 5.4+, a Lua 5.1 compatibility shim will be provided
 so that old plugins continue to work transparently.
 
+                                                                  *lua-luajit*
+Neovim is built with luajit on platforms which support it, which provides
+extra functionality. Lua code in |init.lua| and plugins can assume its presence
+on installations on common platforms. For maximum compatibility with less
+common platforms, availability can be checked using the `jit` global variable: >lua
+  if jit then
+    -- code for luajit
+  else
+    -- code for plain lua 5.1
+  end
+<
+                                                                  *lua-bit*
+In particular, the luajit "bit" extension module is _always_ available.
+A fallback implementation is included when nvim is built with PUC lua 5.1,
+and will be transparently used when `require("bit")` is invoked.
+
 ==============================================================================
 LUA CONCEPTS AND IDIOMS                                         *lua-concepts*
 
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 6f505a958a..4dee958108 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -167,6 +167,7 @@ The following new APIs or features were added.
 • |vim.treesitter.language.add()| as a new replacement for
   `vim.treesitter.language.require_language`.
 
+• `require'bit'` is now always available |lua-bit|
 ==============================================================================
 CHANGED FEATURES                                                 *news-changes*
 
diff --git a/src/bit.c b/src/bit.c
new file mode 100644
index 0000000000..85d2414582
--- /dev/null
+++ b/src/bit.c
@@ -0,0 +1,191 @@
+/*
+** Lua BitOp -- a bit operations library for Lua 5.1/5.2.
+** http://bitop.luajit.org/
+**
+** Copyright (C) 2008-2012 Mike Pall. All rights reserved.
+**
+** Permission is hereby granted, free of charge, to any person obtaining
+** a copy of this software and associated documentation files (the
+** "Software"), to deal in the Software without restriction, including
+** without limitation the rights to use, copy, modify, merge, publish,
+** distribute, sublicense, and/or sell copies of the Software, and to
+** permit persons to whom the Software is furnished to do so, subject to
+** the following conditions:
+**
+** The above copyright notice and this permission notice shall be
+** included in all copies or substantial portions of the Software.
+**
+** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**
+** [ MIT license: http://www.opensource.org/licenses/mit-license.php ]
+*/
+
+#define LUA_BITOP_VERSION	"1.0.2"
+
+#define LUA_LIB
+#include "lua.h"
+#include "lauxlib.h"
+
+#include "bit.h"
+
+#ifdef _MSC_VER
+/* MSVC is stuck in the last century and doesn't have C99's stdint.h. */
+typedef __int32 int32_t;
+typedef unsigned __int32 uint32_t;
+typedef unsigned __int64 uint64_t;
+#else
+#include <stdint.h>
+#endif
+
+typedef int32_t SBits;
+typedef uint32_t UBits;
+
+typedef union {
+  lua_Number n;
+#ifdef LUA_NUMBER_DOUBLE
+  uint64_t b;
+#else
+  UBits b;
+#endif
+} BitNum;
+
+/* Convert argument to bit type. */
+static UBits barg(lua_State *L, int idx)
+{
+  BitNum bn;
+  UBits b;
+#if LUA_VERSION_NUM < 502
+  bn.n = lua_tonumber(L, idx);
+#else
+  bn.n = luaL_checknumber(L, idx);
+#endif
+#if defined(LUA_NUMBER_DOUBLE)
+  bn.n += 6755399441055744.0;  /* 2^52+2^51 */
+#ifdef SWAPPED_DOUBLE
+  b = (UBits)(bn.b >> 32);
+#else
+  b = (UBits)bn.b;
+#endif
+#elif defined(LUA_NUMBER_INT) || defined(LUA_NUMBER_LONG) || \
+      defined(LUA_NUMBER_LONGLONG) || defined(LUA_NUMBER_LONG_LONG) || \
+      defined(LUA_NUMBER_LLONG)
+  if (sizeof(UBits) == sizeof(lua_Number))
+    b = bn.b;
+  else
+    b = (UBits)(SBits)bn.n;
+#elif defined(LUA_NUMBER_FLOAT)
+#error "A 'float' lua_Number type is incompatible with this library"
+#else
+#error "Unknown number type, check LUA_NUMBER_* in luaconf.h"
+#endif
+#if LUA_VERSION_NUM < 502
+  if (b == 0 && !lua_isnumber(L, idx)) {
+    luaL_typerror(L, idx, "number");
+  }
+#endif
+  return b;
+}
+
+/* Return bit type. */
+#define BRET(b)  lua_pushnumber(L, (lua_Number)(SBits)(b)); return 1;
+
+static int bit_tobit(lua_State *L) { BRET(barg(L, 1)) }
+static int bit_bnot(lua_State *L) { BRET(~barg(L, 1)) }
+
+#define BIT_OP(func, opr) \
+  static int func(lua_State *L) { int i; UBits b = barg(L, 1); \
+    for (i = lua_gettop(L); i > 1; i--) b opr barg(L, i); BRET(b) }
+BIT_OP(bit_band, &=)
+BIT_OP(bit_bor, |=)
+BIT_OP(bit_bxor, ^=)
+
+#define bshl(b, n)  (b << n)
+#define bshr(b, n)  (b >> n)
+#define bsar(b, n)  ((SBits)b >> n)
+#define brol(b, n)  ((b << n) | (b >> (32-n)))
+#define bror(b, n)  ((b << (32-n)) | (b >> n))
+#define BIT_SH(func, fn) \
+  static int func(lua_State *L) { \
+    UBits b = barg(L, 1); UBits n = barg(L, 2) & 31; BRET(fn(b, n)) }
+BIT_SH(bit_lshift, bshl)
+BIT_SH(bit_rshift, bshr)
+BIT_SH(bit_arshift, bsar)
+BIT_SH(bit_rol, brol)
+BIT_SH(bit_ror, bror)
+
+static int bit_bswap(lua_State *L)
+{
+  UBits b = barg(L, 1);
+  b = (b >> 24) | ((b >> 8) & 0xff00) | ((b & 0xff00) << 8) | (b << 24);
+  BRET(b)
+}
+
+static int bit_tohex(lua_State *L)
+{
+  UBits b = barg(L, 1);
+  SBits n = lua_isnone(L, 2) ? 8 : (SBits)barg(L, 2);
+  const char *hexdigits = "0123456789abcdef";
+  char buf[8];
+  int i;
+  if (n < 0) { n = -n; hexdigits = "0123456789ABCDEF"; }
+  if (n > 8) n = 8;
+  for (i = (int)n; --i >= 0; ) { buf[i] = hexdigits[b & 15]; b >>= 4; }
+  lua_pushlstring(L, buf, (size_t)n);
+  return 1;
+}
+
+static const struct luaL_Reg bit_funcs[] = {
+  { "tobit",	bit_tobit },
+  { "bnot",	bit_bnot },
+  { "band",	bit_band },
+  { "bor",	bit_bor },
+  { "bxor",	bit_bxor },
+  { "lshift",	bit_lshift },
+  { "rshift",	bit_rshift },
+  { "arshift",	bit_arshift },
+  { "rol",	bit_rol },
+  { "ror",	bit_ror },
+  { "bswap",	bit_bswap },
+  { "tohex",	bit_tohex },
+  { NULL, NULL }
+};
+
+/* Signed right-shifts are implementation-defined per C89/C99.
+** But the de facto standard are arithmetic right-shifts on two's
+** complement CPUs. This behaviour is required here, so test for it.
+*/
+#define BAD_SAR		(bsar(-8, 2) != (SBits)-2)
+
+LUALIB_API int luaopen_bit(lua_State *L)
+{
+  UBits b;
+  lua_pushnumber(L, (lua_Number)1437217655L);
+  b = barg(L, -1);
+  if (b != (UBits)1437217655L || BAD_SAR) {  /* Perform a simple self-test. */
+    const char *msg = "compiled with incompatible luaconf.h";
+#ifdef LUA_NUMBER_DOUBLE
+#ifdef _WIN32
+    if (b == (UBits)1610612736L)
+      msg = "use D3DCREATE_FPU_PRESERVE with DirectX";
+#endif
+    if (b == (UBits)1127743488L)
+      msg = "not compiled with SWAPPED_DOUBLE";
+#endif
+    if (BAD_SAR)
+      msg = "arithmetic right-shift broken";
+    luaL_error(L, "bit library self-test failed (%s)", msg);
+  }
+#if LUA_VERSION_NUM < 502
+  luaL_register(L, "bit", bit_funcs);
+#else
+  luaL_newlib(L, bit_funcs);
+#endif
+  return 1;
+}
+
diff --git a/src/bit.h b/src/bit.h
new file mode 100644
index 0000000000..7e54e6d519
--- /dev/null
+++ b/src/bit.h
@@ -0,0 +1,3 @@
+#include <lua.h>
+
+int luaopen_bit(lua_State *L);
diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 329e831b2e..8884273649 100755
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -367,6 +367,12 @@ glob_wrapper(NVIM_HEADERS *.h)
 glob_wrapper(EXTERNAL_SOURCES ../xdiff/*.c ../mpack/*.c ../cjson/*.c ../klib/*.c)
 glob_wrapper(EXTERNAL_HEADERS ../xdiff/*.h ../mpack/*.h ../cjson/*.h ../klib/*.h)
 
+if(PREFER_LUA)
+  # luajit not used, use a vendored copy of the bit module
+  list(APPEND EXTERNAL_SOURCES ${PROJECT_SOURCE_DIR}/src/bit.c)
+  target_compile_definitions(main_lib INTERFACE NVIM_VENDOR_BIT)
+endif()
+
 foreach(subdir
         os
         api
@@ -425,7 +431,7 @@ if(MSVC)
     ${EXTERNAL_SOURCES} PROPERTIES COMPILE_FLAGS "${COMPILE_FLAGS} -wd4090 -wd4244 -wd4267")
 else()
   set_source_files_properties(
-    ${EXTERNAL_SOURCES} PROPERTIES COMPILE_FLAGS "${COMPILE_FLAGS} -Wno-conversion -Wno-missing-noreturn -Wno-missing-format-attribute -Wno-double-promotion -Wno-strict-prototypes")
+    ${EXTERNAL_SOURCES} PROPERTIES COMPILE_FLAGS "${COMPILE_FLAGS} -Wno-conversion -Wno-missing-noreturn -Wno-missing-format-attribute -Wno-double-promotion -Wno-strict-prototypes -Wno-misleading-indentation")
 endif()
 
 # Log level (MIN_LOG_LEVEL in log.h)
@@ -684,8 +690,8 @@ if(UNIX)
   endif()
 endif()
 
-if(NOT LUAJIT_FOUND)
-  message(STATUS "luajit not found, skipping unit tests")
+if(PREFER_LUA)
+  message(STATUS "luajit not used, skipping unit tests")
 else()
   glob_wrapper(UNIT_TEST_FIXTURES ${PROJECT_SOURCE_DIR}/test/unit/fixtures/*.c)
   target_sources(nvim PRIVATE $<$<CONFIG:Debug>:${UNIT_TEST_FIXTURES}>)
diff --git a/src/nvim/lua/stdlib.c b/src/nvim/lua/stdlib.c
index 5aeff4de98..d9682ff63d 100644
--- a/src/nvim/lua/stdlib.c
+++ b/src/nvim/lua/stdlib.c
@@ -11,6 +11,10 @@
 #include <string.h>
 #include <sys/types.h>
 
+#ifdef NVIM_VENDOR_BIT
+# include "bit.h"
+#endif
+
 #include "auto/config.h"
 #include "cjson/lua_cjson.h"
 #include "mpack/lmpack.h"
@@ -596,6 +600,13 @@ void nlua_state_add_stdlib(lua_State *const lstate, bool is_thread)
   // vim.json
   lua_cjson_new(lstate);
   lua_setfield(lstate, -2, "json");
+
+#ifdef NVIM_VENDOR_BIT
+  // if building with puc lua, use internal fallback for require'bit'
+  int top = lua_gettop(lstate);
+  luaopen_bit(lstate);
+  lua_settop(lstate, top);
+#endif
 }
 
 /// like luaL_error, but allow cleanup
diff --git a/test/functional/lua/overrides_spec.lua b/test/functional/lua/overrides_spec.lua
index 3f107811ae..f88698f83d 100644
--- a/test/functional/lua/overrides_spec.lua
+++ b/test/functional/lua/overrides_spec.lua
@@ -338,3 +338,11 @@ describe('os.getenv', function()
     eq(value, funcs.luaeval('os.getenv("XTEST_1")'))
   end)
 end)
+
+-- "bit" module is always available, regardless if nvim is built with
+-- luajit or PUC lua 5.1.
+describe('bit module', function()
+  it('works', function()
+    eq (9, exec_lua [[ return require'bit'.band(11,13) ]])
+  end)
+end)