build & link with luajit instead of lua5.1

1 files changed, 705 insertions, 0 deletions

diff --git a/libs/luajit-cmake/luajit/src/jit/bcsave.lua b/libs/luajit-cmake/luajit/src/jit/bcsave.lua
new file mode 100644
index 0000000..90fe9da
--- /dev/null
+++ b/libs/luajit-cmake/luajit/src/jit/bcsave.lua
@@ -0,0 +1,705 @@
+----------------------------------------------------------------------------
+-- LuaJIT module to save/list bytecode.
+--
+-- Copyright (C) 2005-2022 Mike Pall. All rights reserved.
+-- Released under the MIT license. See Copyright Notice in luajit.h
+----------------------------------------------------------------------------
+--
+-- This module saves or lists the bytecode for an input file.
+-- It's run by the -b command line option.
+--
+------------------------------------------------------------------------------
+
+local jit = require("jit")
+assert(jit.version_num == 20100, "LuaJIT core/library version mismatch")
+local bit = require("bit")
+
+-- Symbol name prefix for LuaJIT bytecode.
+local LJBC_PREFIX = "luaJIT_BC_"
+
+local type, assert = type, assert
+local format = string.format
+local tremove, tconcat = table.remove, table.concat
+
+------------------------------------------------------------------------------
+
+local function usage()
+  io.stderr:write[[
+Save LuaJIT bytecode: luajit -b[options] input output
+  -l        Only list bytecode.
+  -s        Strip debug info (default).
+  -g        Keep debug info.
+  -n name   Set module name (default: auto-detect from input name).
+  -t type   Set output file type (default: auto-detect from output name).
+  -a arch   Override architecture for object files (default: native).
+  -o os     Override OS for object files (default: native).
+  -F name   Override filename (default: input filename).
+  -e chunk  Use chunk string as input.
+  --        Stop handling options.
+  -         Use stdin as input and/or stdout as output.
+
+File types: c h obj o raw (default)
+]]
+  os.exit(1)
+end
+
+local function check(ok, ...)
+  if ok then return ok, ... end
+  io.stderr:write("luajit: ", ...)
+  io.stderr:write("\n")
+  os.exit(1)
+end
+
+local function readfile(ctx, input)
+  if type(input) == "function" then return input end
+  if ctx.filename then
+    local data
+    if input == "-" then
+      data = io.stdin:read("*a")
+    else
+      local fp = assert(io.open(input, "rb"))
+      data = assert(fp:read("*a"))
+      assert(fp:close())
+    end
+    return check(load(data, ctx.filename))
+  else
+    if input == "-" then input = nil end
+    return check(loadfile(input))
+  end
+end
+
+local function savefile(name, mode)
+  if name == "-" then return io.stdout end
+  return check(io.open(name, mode))
+end
+
+local function set_stdout_binary(ffi)
+  ffi.cdef[[int _setmode(int fd, int mode);]]
+  ffi.C._setmode(1, 0x8000)
+end
+
+------------------------------------------------------------------------------
+
+local map_type = {
+  raw = "raw", c = "c", h = "h", o = "obj", obj = "obj",
+}
+
+local map_arch = {
+  x86 =		{ e = "le", b = 32, m = 3, p = 0x14c, },
+  x64 =		{ e = "le", b = 64, m = 62, p = 0x8664, },
+  arm =		{ e = "le", b = 32, m = 40, p = 0x1c0, },
+  arm64 =	{ e = "le", b = 64, m = 183, p = 0xaa64, },
+  arm64be =	{ e = "be", b = 64, m = 183, },
+  ppc =		{ e = "be", b = 32, m = 20, },
+  mips =	{ e = "be", b = 32, m = 8, f = 0x50001006, },
+  mipsel =	{ e = "le", b = 32, m = 8, f = 0x50001006, },
+  mips64 =	{ e = "be", b = 64, m = 8, f = 0x80000007, },
+  mips64el =	{ e = "le", b = 64, m = 8, f = 0x80000007, },
+  mips64r6 =	{ e = "be", b = 64, m = 8, f = 0xa0000407, },
+  mips64r6el =	{ e = "le", b = 64, m = 8, f = 0xa0000407, },
+}
+
+local map_os = {
+  linux = true, windows = true, osx = true, freebsd = true, netbsd = true,
+  openbsd = true, dragonfly = true, solaris = true,
+}
+
+local function checkarg(str, map, err)
+  str = str:lower()
+  local s = check(map[str], "unknown ", err)
+  return type(s) == "string" and s or str
+end
+
+local function detecttype(str)
+  local ext = str:lower():match("%.(%a+)$")
+  return map_type[ext] or "raw"
+end
+
+local function checkmodname(str)
+  check(str:match("^[%w_.%-]+$"), "bad module name")
+  return str:gsub("[%.%-]", "_")
+end
+
+local function detectmodname(str)
+  if type(str) == "string" then
+    local tail = str:match("[^/\\]+$")
+    if tail then str = tail end
+    local head = str:match("^(.*)%.[^.]*$")
+    if head then str = head end
+    str = str:match("^[%w_.%-]+")
+  else
+    str = nil
+  end
+  check(str, "cannot derive module name, use -n name")
+  return str:gsub("[%.%-]", "_")
+end
+
+------------------------------------------------------------------------------
+
+local function bcsave_tail(fp, output, s)
+  local ok, err = fp:write(s)
+  if ok and output ~= "-" then ok, err = fp:close() end
+  check(ok, "cannot write ", output, ": ", err)
+end
+
+local function bcsave_raw(output, s)
+  if output == "-" and jit.os == "Windows" then
+    local ok, ffi = pcall(require, "ffi")
+    check(ok, "FFI library required to write binary file to stdout")
+    set_stdout_binary(ffi)
+  end
+  local fp = savefile(output, "wb")
+  bcsave_tail(fp, output, s)
+end
+
+local function bcsave_c(ctx, output, s)
+  local fp = savefile(output, "w")
+  if ctx.type == "c" then
+    fp:write(format([[
+#ifdef __cplusplus
+extern "C"
+#endif
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+const unsigned char %s%s[] = {
+]], LJBC_PREFIX, ctx.modname))
+  else
+    fp:write(format([[
+#define %s%s_SIZE %d
+static const unsigned char %s%s[] = {
+]], LJBC_PREFIX, ctx.modname, #s, LJBC_PREFIX, ctx.modname))
+  end
+  local t, n, m = {}, 0, 0
+  for i=1,#s do
+    local b = tostring(string.byte(s, i))
+    m = m + #b + 1
+    if m > 78 then
+      fp:write(tconcat(t, ",", 1, n), ",\n")
+      n, m = 0, #b + 1
+    end
+    n = n + 1
+    t[n] = b
+  end
+  bcsave_tail(fp, output, tconcat(t, ",", 1, n).."\n};\n")
+end
+
+local function bcsave_elfobj(ctx, output, s, ffi)
+  ffi.cdef[[
+typedef struct {
+  uint8_t emagic[4], eclass, eendian, eversion, eosabi, eabiversion, epad[7];
+  uint16_t type, machine;
+  uint32_t version;
+  uint32_t entry, phofs, shofs;
+  uint32_t flags;
+  uint16_t ehsize, phentsize, phnum, shentsize, shnum, shstridx;
+} ELF32header;
+typedef struct {
+  uint8_t emagic[4], eclass, eendian, eversion, eosabi, eabiversion, epad[7];
+  uint16_t type, machine;
+  uint32_t version;
+  uint64_t entry, phofs, shofs;
+  uint32_t flags;
+  uint16_t ehsize, phentsize, phnum, shentsize, shnum, shstridx;
+} ELF64header;
+typedef struct {
+  uint32_t name, type, flags, addr, ofs, size, link, info, align, entsize;
+} ELF32sectheader;
+typedef struct {
+  uint32_t name, type;
+  uint64_t flags, addr, ofs, size;
+  uint32_t link, info;
+  uint64_t align, entsize;
+} ELF64sectheader;
+typedef struct {
+  uint32_t name, value, size;
+  uint8_t info, other;
+  uint16_t sectidx;
+} ELF32symbol;
+typedef struct {
+  uint32_t name;
+  uint8_t info, other;
+  uint16_t sectidx;
+  uint64_t value, size;
+} ELF64symbol;
+typedef struct {
+  ELF32header hdr;
+  ELF32sectheader sect[6];
+  ELF32symbol sym[2];
+  uint8_t space[4096];
+} ELF32obj;
+typedef struct {
+  ELF64header hdr;
+  ELF64sectheader sect[6];
+  ELF64symbol sym[2];
+  uint8_t space[4096];
+} ELF64obj;
+]]
+  local symname = LJBC_PREFIX..ctx.modname
+  local ai = assert(map_arch[ctx.arch])
+  local is64, isbe = ai.b == 64, ai.e == "be"
+
+  -- Handle different host/target endianess.
+  local function f32(x) return x end
+  local f16, fofs = f32, f32
+  if ffi.abi("be") ~= isbe then
+    f32 = bit.bswap
+    function f16(x) return bit.rshift(bit.bswap(x), 16) end
+    if is64 then
+      local two32 = ffi.cast("int64_t", 2^32)
+      function fofs(x) return bit.bswap(x)*two32 end
+    else
+      fofs = f32
+    end
+  end
+
+  -- Create ELF object and fill in header.
+  local o = ffi.new(is64 and "ELF64obj" or "ELF32obj")
+  local hdr = o.hdr
+  if ctx.os == "bsd" or ctx.os == "other" then -- Determine native hdr.eosabi.
+    local bf = assert(io.open("/bin/ls", "rb"))
+    local bs = bf:read(9)
+    bf:close()
+    ffi.copy(o, bs, 9)
+    check(hdr.emagic[0] == 127, "no support for writing native object files")
+  else
+    hdr.emagic = "\127ELF"
+    hdr.eosabi = ({ freebsd=9, netbsd=2, openbsd=12, solaris=6 })[ctx.os] or 0
+  end
+  hdr.eclass = is64 and 2 or 1
+  hdr.eendian = isbe and 2 or 1
+  hdr.eversion = 1
+  hdr.type = f16(1)
+  hdr.machine = f16(ai.m)
+  hdr.flags = f32(ai.f or 0)
+  hdr.version = f32(1)
+  hdr.shofs = fofs(ffi.offsetof(o, "sect"))
+  hdr.ehsize = f16(ffi.sizeof(hdr))
+  hdr.shentsize = f16(ffi.sizeof(o.sect[0]))
+  hdr.shnum = f16(6)
+  hdr.shstridx = f16(2)
+
+  -- Fill in sections and symbols.
+  local sofs, ofs = ffi.offsetof(o, "space"), 1
+  for i,name in ipairs{
+      ".symtab", ".shstrtab", ".strtab", ".rodata", ".note.GNU-stack",
+    } do
+    local sect = o.sect[i]
+    sect.align = fofs(1)
+    sect.name = f32(ofs)
+    ffi.copy(o.space+ofs, name)
+    ofs = ofs + #name+1
+  end
+  o.sect[1].type = f32(2) -- .symtab
+  o.sect[1].link = f32(3)
+  o.sect[1].info = f32(1)
+  o.sect[1].align = fofs(8)
+  o.sect[1].ofs = fofs(ffi.offsetof(o, "sym"))
+  o.sect[1].entsize = fofs(ffi.sizeof(o.sym[0]))
+  o.sect[1].size = fofs(ffi.sizeof(o.sym))
+  o.sym[1].name = f32(1)
+  o.sym[1].sectidx = f16(4)
+  o.sym[1].size = fofs(#s)
+  o.sym[1].info = 17
+  o.sect[2].type = f32(3) -- .shstrtab
+  o.sect[2].ofs = fofs(sofs)
+  o.sect[2].size = fofs(ofs)
+  o.sect[3].type = f32(3) -- .strtab
+  o.sect[3].ofs = fofs(sofs + ofs)
+  o.sect[3].size = fofs(#symname+2)
+  ffi.copy(o.space+ofs+1, symname)
+  ofs = ofs + #symname + 2
+  o.sect[4].type = f32(1) -- .rodata
+  o.sect[4].flags = fofs(2)
+  o.sect[4].ofs = fofs(sofs + ofs)
+  o.sect[4].size = fofs(#s)
+  o.sect[5].type = f32(1) -- .note.GNU-stack
+  o.sect[5].ofs = fofs(sofs + ofs + #s)
+
+  -- Write ELF object file.
+  local fp = savefile(output, "wb")
+  fp:write(ffi.string(o, ffi.sizeof(o)-4096+ofs))
+  bcsave_tail(fp, output, s)
+end
+
+local function bcsave_peobj(ctx, output, s, ffi)
+  ffi.cdef[[
+typedef struct {
+  uint16_t arch, nsects;
+  uint32_t time, symtabofs, nsyms;
+  uint16_t opthdrsz, flags;
+} PEheader;
+typedef struct {
+  char name[8];
+  uint32_t vsize, vaddr, size, ofs, relocofs, lineofs;
+  uint16_t nreloc, nline;
+  uint32_t flags;
+} PEsection;
+typedef struct __attribute((packed)) {
+  union {
+    char name[8];
+    uint32_t nameref[2];
+  };
+  uint32_t value;
+  int16_t sect;
+  uint16_t type;
+  uint8_t scl, naux;
+} PEsym;
+typedef struct __attribute((packed)) {
+  uint32_t size;
+  uint16_t nreloc, nline;
+  uint32_t cksum;
+  uint16_t assoc;
+  uint8_t comdatsel, unused[3];
+} PEsymaux;
+typedef struct {
+  PEheader hdr;
+  PEsection sect[2];
+  // Must be an even number of symbol structs.
+  PEsym sym0;
+  PEsymaux sym0aux;
+  PEsym sym1;
+  PEsymaux sym1aux;
+  PEsym sym2;
+  PEsym sym3;
+  uint32_t strtabsize;
+  uint8_t space[4096];
+} PEobj;
+]]
+  local symname = LJBC_PREFIX..ctx.modname
+  local ai = assert(map_arch[ctx.arch])
+  local is64 = ai.b == 64
+  local symexport = "   /EXPORT:"..symname..",DATA "
+
+  -- The file format is always little-endian. Swap if the host is big-endian.
+  local function f32(x) return x end
+  local f16 = f32
+  if ffi.abi("be") then
+    f32 = bit.bswap
+    function f16(x) return bit.rshift(bit.bswap(x), 16) end
+  end
+
+  -- Create PE object and fill in header.
+  local o = ffi.new("PEobj")
+  local hdr = o.hdr
+  hdr.arch = f16(assert(ai.p))
+  hdr.nsects = f16(2)
+  hdr.symtabofs = f32(ffi.offsetof(o, "sym0"))
+  hdr.nsyms = f32(6)
+
+  -- Fill in sections and symbols.
+  o.sect[0].name = ".drectve"
+  o.sect[0].size = f32(#symexport)
+  o.sect[0].flags = f32(0x00100a00)
+  o.sym0.sect = f16(1)
+  o.sym0.scl = 3
+  o.sym0.name = ".drectve"
+  o.sym0.naux = 1
+  o.sym0aux.size = f32(#symexport)
+  o.sect[1].name = ".rdata"
+  o.sect[1].size = f32(#s)
+  o.sect[1].flags = f32(0x40300040)
+  o.sym1.sect = f16(2)
+  o.sym1.scl = 3
+  o.sym1.name = ".rdata"
+  o.sym1.naux = 1
+  o.sym1aux.size = f32(#s)
+  o.sym2.sect = f16(2)
+  o.sym2.scl = 2
+  o.sym2.nameref[1] = f32(4)
+  o.sym3.sect = f16(-1)
+  o.sym3.scl = 2
+  o.sym3.value = f32(1)
+  o.sym3.name = "@feat.00" -- Mark as SafeSEH compliant.
+  ffi.copy(o.space, symname)
+  local ofs = #symname + 1
+  o.strtabsize = f32(ofs + 4)
+  o.sect[0].ofs = f32(ffi.offsetof(o, "space") + ofs)
+  ffi.copy(o.space + ofs, symexport)
+  ofs = ofs + #symexport
+  o.sect[1].ofs = f32(ffi.offsetof(o, "space") + ofs)
+
+  -- Write PE object file.
+  local fp = savefile(output, "wb")
+  fp:write(ffi.string(o, ffi.sizeof(o)-4096+ofs))
+  bcsave_tail(fp, output, s)
+end
+
+local function bcsave_machobj(ctx, output, s, ffi)
+  ffi.cdef[[
+typedef struct
+{
+  uint32_t magic, cputype, cpusubtype, filetype, ncmds, sizeofcmds, flags;
+} mach_header;
+typedef struct
+{
+  mach_header; uint32_t reserved;
+} mach_header_64;
+typedef struct {
+  uint32_t cmd, cmdsize;
+  char segname[16];
+  uint32_t vmaddr, vmsize, fileoff, filesize;
+  uint32_t maxprot, initprot, nsects, flags;
+} mach_segment_command;
+typedef struct {
+  uint32_t cmd, cmdsize;
+  char segname[16];
+  uint64_t vmaddr, vmsize, fileoff, filesize;
+  uint32_t maxprot, initprot, nsects, flags;
+} mach_segment_command_64;
+typedef struct {
+  char sectname[16], segname[16];
+  uint32_t addr, size;
+  uint32_t offset, align, reloff, nreloc, flags;
+  uint32_t reserved1, reserved2;
+} mach_section;
+typedef struct {
+  char sectname[16], segname[16];
+  uint64_t addr, size;
+  uint32_t offset, align, reloff, nreloc, flags;
+  uint32_t reserved1, reserved2, reserved3;
+} mach_section_64;
+typedef struct {
+  uint32_t cmd, cmdsize, symoff, nsyms, stroff, strsize;
+} mach_symtab_command;
+typedef struct {
+  int32_t strx;
+  uint8_t type, sect;
+  int16_t desc;
+  uint32_t value;
+} mach_nlist;
+typedef struct {
+  int32_t strx;
+  uint8_t type, sect;
+  uint16_t desc;
+  uint64_t value;
+} mach_nlist_64;
+typedef struct
+{
+  int32_t magic, nfat_arch;
+} mach_fat_header;
+typedef struct
+{
+  int32_t cputype, cpusubtype, offset, size, align;
+} mach_fat_arch;
+typedef struct {
+  struct {
+    mach_header hdr;
+    mach_segment_command seg;
+    mach_section sec;
+    mach_symtab_command sym;
+  } arch[1];
+  mach_nlist sym_entry;
+  uint8_t space[4096];
+} mach_obj;
+typedef struct {
+  struct {
+    mach_header_64 hdr;
+    mach_segment_command_64 seg;
+    mach_section_64 sec;
+    mach_symtab_command sym;
+  } arch[1];
+  mach_nlist_64 sym_entry;
+  uint8_t space[4096];
+} mach_obj_64;
+typedef struct {
+  mach_fat_header fat;
+  mach_fat_arch fat_arch[2];
+  struct {
+    mach_header hdr;
+    mach_segment_command seg;
+    mach_section sec;
+    mach_symtab_command sym;
+  } arch[2];
+  mach_nlist sym_entry;
+  uint8_t space[4096];
+} mach_fat_obj;
+typedef struct {
+  mach_fat_header fat;
+  mach_fat_arch fat_arch[2];
+  struct {
+    mach_header_64 hdr;
+    mach_segment_command_64 seg;
+    mach_section_64 sec;
+    mach_symtab_command sym;
+  } arch[2];
+  mach_nlist_64 sym_entry;
+  uint8_t space[4096];
+} mach_fat_obj_64;
+]]
+  local symname = '_'..LJBC_PREFIX..ctx.modname
+  local isfat, is64, align, mobj = false, false, 4, "mach_obj"
+  if ctx.arch == "x64" then
+    is64, align, mobj = true, 8, "mach_obj_64"
+  elseif ctx.arch == "arm" then
+    isfat, mobj = true, "mach_fat_obj"
+  elseif ctx.arch == "arm64" then
+    is64, align, isfat, mobj = true, 8, true, "mach_fat_obj_64"
+  else
+    check(ctx.arch == "x86", "unsupported architecture for OSX")
+  end
+  local function aligned(v, a) return bit.band(v+a-1, -a) end
+  local be32 = bit.bswap -- Mach-O FAT is BE, supported archs are LE.
+
+  -- Create Mach-O object and fill in header.
+  local o = ffi.new(mobj)
+  local mach_size = aligned(ffi.offsetof(o, "space")+#symname+2, align)
+  local cputype = ({ x86={7}, x64={0x01000007}, arm={7,12}, arm64={0x01000007,0x0100000c} })[ctx.arch]
+  local cpusubtype = ({ x86={3}, x64={3}, arm={3,9}, arm64={3,0} })[ctx.arch]
+  if isfat then
+    o.fat.magic = be32(0xcafebabe)
+    o.fat.nfat_arch = be32(#cpusubtype)
+  end
+
+  -- Fill in sections and symbols.
+  for i=0,#cpusubtype-1 do
+    local ofs = 0
+    if isfat then
+      local a = o.fat_arch[i]
+      a.cputype = be32(cputype[i+1])
+      a.cpusubtype = be32(cpusubtype[i+1])
+      -- Subsequent slices overlap each other to share data.
+      ofs = ffi.offsetof(o, "arch") + i*ffi.sizeof(o.arch[0])
+      a.offset = be32(ofs)
+      a.size = be32(mach_size-ofs+#s)
+    end
+    local a = o.arch[i]
+    a.hdr.magic = is64 and 0xfeedfacf or 0xfeedface
+    a.hdr.cputype = cputype[i+1]
+    a.hdr.cpusubtype = cpusubtype[i+1]
+    a.hdr.filetype = 1
+    a.hdr.ncmds = 2
+    a.hdr.sizeofcmds = ffi.sizeof(a.seg)+ffi.sizeof(a.sec)+ffi.sizeof(a.sym)
+    a.seg.cmd = is64 and 0x19 or 0x1
+    a.seg.cmdsize = ffi.sizeof(a.seg)+ffi.sizeof(a.sec)
+    a.seg.vmsize = #s
+    a.seg.fileoff = mach_size-ofs
+    a.seg.filesize = #s
+    a.seg.maxprot = 1
+    a.seg.initprot = 1
+    a.seg.nsects = 1
+    ffi.copy(a.sec.sectname, "__data")
+    ffi.copy(a.sec.segname, "__DATA")
+    a.sec.size = #s
+    a.sec.offset = mach_size-ofs
+    a.sym.cmd = 2
+    a.sym.cmdsize = ffi.sizeof(a.sym)
+    a.sym.symoff = ffi.offsetof(o, "sym_entry")-ofs
+    a.sym.nsyms = 1
+    a.sym.stroff = ffi.offsetof(o, "sym_entry")+ffi.sizeof(o.sym_entry)-ofs
+    a.sym.strsize = aligned(#symname+2, align)
+  end
+  o.sym_entry.type = 0xf
+  o.sym_entry.sect = 1
+  o.sym_entry.strx = 1
+  ffi.copy(o.space+1, symname)
+
+  -- Write Macho-O object file.
+  local fp = savefile(output, "wb")
+  fp:write(ffi.string(o, mach_size))
+  bcsave_tail(fp, output, s)
+end
+
+local function bcsave_obj(ctx, output, s)
+  local ok, ffi = pcall(require, "ffi")
+  check(ok, "FFI library required to write this file type")
+  if output == "-" and jit.os == "Windows" then
+    set_stdout_binary(ffi)
+  end
+  if ctx.os == "windows" then
+    return bcsave_peobj(ctx, output, s, ffi)
+  elseif ctx.os == "osx" then
+    return bcsave_machobj(ctx, output, s, ffi)
+  else
+    return bcsave_elfobj(ctx, output, s, ffi)
+  end
+end
+
+------------------------------------------------------------------------------
+
+local function bclist(ctx, input, output)
+  local f = readfile(ctx, input)
+  require("jit.bc").dump(f, savefile(output, "w"), true)
+end
+
+local function bcsave(ctx, input, output)
+  local f = readfile(ctx, input)
+  local s = string.dump(f, ctx.strip)
+  local t = ctx.type
+  if not t then
+    t = detecttype(output)
+    ctx.type = t
+  end
+  if t == "raw" then
+    bcsave_raw(output, s)
+  else
+    if not ctx.modname then ctx.modname = detectmodname(input) end
+    if t == "obj" then
+      bcsave_obj(ctx, output, s)
+    else
+      bcsave_c(ctx, output, s)
+    end
+  end
+end
+
+local function docmd(...)
+  local arg = {...}
+  local n = 1
+  local list = false
+  local ctx = {
+    strip = true, arch = jit.arch, os = jit.os:lower(),
+    type = false, modname = false,
+  }
+  while n <= #arg do
+    local a = arg[n]
+    if type(a) == "string" and a:sub(1, 1) == "-" and a ~= "-" then
+      tremove(arg, n)
+      if a == "--" then break end
+      for m=2,#a do
+	local opt = a:sub(m, m)
+	if opt == "l" then
+	  list = true
+	elseif opt == "s" then
+	  ctx.strip = true
+	elseif opt == "g" then
+	  ctx.strip = false
+	else
+	  if arg[n] == nil or m ~= #a then usage() end
+	  if opt == "e" then
+	    if n ~= 1 then usage() end
+	    arg[1] = check(loadstring(arg[1]))
+	  elseif opt == "n" then
+	    ctx.modname = checkmodname(tremove(arg, n))
+	  elseif opt == "t" then
+	    ctx.type = checkarg(tremove(arg, n), map_type, "file type")
+	  elseif opt == "a" then
+	    ctx.arch = checkarg(tremove(arg, n), map_arch, "architecture")
+	  elseif opt == "o" then
+	    ctx.os = checkarg(tremove(arg, n), map_os, "OS name")
+	  elseif opt == "F" then
+	    ctx.filename = "@"..tremove(arg, n)
+	  else
+	    usage()
+	  end
+	end
+      end
+    else
+      n = n + 1
+    end
+  end
+  if list then
+    if #arg == 0 or #arg > 2 then usage() end
+    bclist(ctx, arg[1], arg[2] or "-")
+  else
+    if #arg ~= 2 then usage() end
+    bcsave(ctx, arg[1], arg[2])
+  end
+end
+
+------------------------------------------------------------------------------
+
+-- Public module functions.
+return {
+  start = docmd -- Process -b command line option.
+}
+