feat: add stdlib IO and extern function support

- Add stdlib/io.c with PrintLine, Print, PrintInt, PrintFloat, PrintBool, ReadLine
- Support extern function declarations (functions without body)
- Generate C forward declarations for extern functions
- Map Bux type names (String, int, etc.) to C types in codegen
- Update build system to copy all stdlib files
- Hello World example works: prints 'Hello, Bux!'

src/c_backend.nim

@@ -64,7 +64,24 @@ proc typeToC*(typ: Type): string =
     if typ.inner.len > 0:
       return typeToC(typ.inner[0]) & "*"
     return "void*"
-  of tkNamed: return typ.name
+  of tkNamed:
+    # Map common Bux type names to C types
+    case typ.name
+    of "String", "str": return "const char*"
+    of "int": return "int"
+    of "int8": return "int8_t"
+    of "int16": return "int16_t"
+    of "int32": return "int32_t"
+    of "int64": return "int64_t"
+    of "uint": return "unsigned int"
+    of "uint8": return "uint8_t"
+    of "uint16": return "uint16_t"
+    of "uint32": return "uint32_t"
+    of "uint64": return "uint64_t"
+    of "float32": return "float"
+    of "float64": return "double"
+    of "bool": return "bool"
+    else: return typ.name
   of tkTuple: return "void*"  # TODO: proper tuple struct
   of tkFunc: return "void*"  # TODO: function pointer
   else: return "int"
@@ -344,6 +361,16 @@ proc emitEnum*(be: var CBackend, name: string, variants: seq[string]) =
   be.emitLine(&"}} {name};")
   be.emitLine("")
 
+proc emitExternDecl*(be: var CBackend, efunc: HirFunc) =
+  let retType = typeToC(efunc.retType)
+  var params: seq[string] = @[]
+  for p in efunc.params:
+    params.add(&"{typeToC(p.typ)} {p.name}")
+  if params.len == 0:
+    params.add("void")
+  let paramsStr = params.join(", ")
+  be.emitLine(&"extern {retType} {efunc.name}({paramsStr});")
+
 proc emitModule*(be: var CBackend, module: HirModule): string =
   # Header
   be.emitLine("/* Generated by Bux Compiler */")
@@ -360,6 +387,13 @@ proc emitModule*(be: var CBackend, module: HirModule): string =
   if module.structs.len > 0:
     be.emitLine("")
 
+  # Extern function declarations
+  if module.externFuncs.len > 0:
+    be.emitLine("/* Extern function declarations */")
+    for ef in module.externFuncs:
+      be.emitExternDecl(ef)
+    be.emitLine("")
+
   # Struct definitions
   for s in module.structs:
     be.emitStruct(s.name, s.fields)

src/cli.nim

@@ -256,30 +256,45 @@ proc cmdBuild*(args: seq[string], opts: GlobalOptions): int =
   let cFile = buildDir / "main.c"
   writeFile(cFile, allCCode)
 
-  # Copy runtime
+  # Copy runtime and stdlib files
   let runtimeDst = buildDir / "runtime.c"
-  var runtimeFound = false
-  # Search in multiple locations
-  let searchPaths = @[
-    getAppDir() / ".." / "stdlib" / "runtime.c",
-    getAppDir() / "stdlib" / "runtime.c",
-    root / "stdlib" / "runtime.c",
-    root / "stdlib_runtime.c",
-    "/home/ziko/z-git/bux/bux/stdlib/runtime.c",  # TODO: make this configurable
+  let ioDst = buildDir / "io.c"
+  var stdlibDir = ""
+  # Search for stdlib directory
+  let stdlibSearchPaths = @[
+    getAppDir() / ".." / "stdlib",
+    getAppDir() / "stdlib",
+    root / "stdlib",
+    "/home/ziko/z-git/bux/bux/stdlib",  # TODO: make this configurable
   ]
-  for runtimePath in searchPaths:
-    if fileExists(runtimePath):
-      copyFile(runtimePath, runtimeDst)
-      runtimeFound = true
+  for path in stdlibSearchPaths:
+    if dirExists(path):
+      stdlibDir = path
       break
-  if not runtimeFound:
-    printError("runtime.c not found (searched in stdlib/, build/, and project root)", useColor)
+  if stdlibDir == "":
+    printError("stdlib directory not found", useColor)
+    return 1
+  
+  # Copy runtime.c
+  let runtimeSrc = stdlibDir / "runtime.c"
+  if fileExists(runtimeSrc):
+    copyFile(runtimeSrc, runtimeDst)
+  else:
+    printError("runtime.c not found in stdlib", useColor)
+    return 1
+  
+  # Copy io.c
+  let ioSrc = stdlibDir / "io.c"
+  if fileExists(ioSrc):
+    copyFile(ioSrc, ioDst)
+  else:
+    printError("io.c not found in stdlib", useColor)
     return 1
 
   # Compile with cc
   let outputName = if man.name != "": man.name else: "bux_out"
   let outputFile = buildDir / outputName
-  let ccCmd = &"cc -o {outputFile} {cFile} {runtimeDst} -lm 2>&1"
+  let ccCmd = &"cc -o {outputFile} {cFile} {runtimeDst} {ioDst} -lm 2>&1"
   if opts.verbose:
     printInfo(&"running: {ccCmd}", useColor)
   let (output, exitCode) = execCmdEx(ccCmd)

src/hir.nim

@@ -126,6 +126,7 @@ type
 
   HirModule* = object
     funcs*: seq[HirFunc]
+    externFuncs*: seq[HirFunc]  # Functions declared with extern (no body)
     structs*: seq[tuple[name: string, fields: seq[tuple[name: string, typ: Type]]]]
     enums*: seq[tuple[name: string, variants: seq[string]]]
     consts*: seq[tuple[name: string, typ: Type, value: HirNode]]

src/hir_lower.nim

@@ -420,6 +420,7 @@ proc lowerFunc*(ctx: var LowerCtx, decl: Decl): HirFunc =
 proc lowerModule*(module: Module, sema: Sema): HirModule =
   var ctx = initLowerCtx(module, sema)
   var funcs: seq[HirFunc] = @[]
+  var externFuncs: seq[HirFunc] = @[]
   var structs: seq[tuple[name: string, fields: seq[tuple[name: string, typ: Type]]]] = @[]
   var enums: seq[tuple[name: string, variants: seq[string]]] = @[]
   var consts: seq[tuple[name: string, typ: Type, value: HirNode]] = @[]
@@ -427,7 +428,11 @@ proc lowerModule*(module: Module, sema: Sema): HirModule =
   for decl in module.items:
     case decl.kind
     of dkFunc:
-      funcs.add(ctx.lowerFunc(decl))
+      if decl.declFuncBody != nil:
+        funcs.add(ctx.lowerFunc(decl))
+      else:
+        # Extern function (no body)
+        externFuncs.add(ctx.lowerFunc(decl))
     of dkImpl:
       for methodDecl in decl.declImplMethods:
         if methodDecl.kind == dkFunc:
@@ -461,4 +466,4 @@ proc lowerModule*(module: Module, sema: Sema): HirModule =
       consts.add((decl.declConstName, typ, value))
     else: discard
 
-  result = HirModule(funcs: funcs, structs: structs, enums: enums, consts: consts)
+  result = HirModule(funcs: funcs, externFuncs: externFuncs, structs: structs, enums: enums, consts: consts)