diff --git a/ast.h b/ast.h
index 175ce6f..ec2d0fa 100644
--- a/ast.h
+++ b/ast.h
@@ -45,6 +45,7 @@ struct AstStmt {
 typedef enum : unsigned int {
     AstSpec_Int = 1 << 0,
     AstSpec_Char = 1 << 1,
+    AstSpec_Void = 1 << 2,
     AstSpec_DefTy = 1 << 6,
     AstSpec_Unsigned = 1 << 7,
     AstSpec_Static = 1 << 8,
diff --git a/ast_print.c b/ast_print.c
index 76f5f16..fd4334a 100644
--- a/ast_print.c
+++ b/ast_print.c
@@ -262,7 +262,7 @@ void ast_expr_print(FILE* f, const AstExpr* node, int depth)
                 }
                 indent(f, depth + 1);
             }
-            fprintf(f, ",]\n");
+            fprintf(f, "],\n");
 
             indent(f, depth);
             fprintf(f, "}");
diff --git a/parse.c b/parse.c
index 88b891a..0de34b9 100644
--- a/parse.c
+++ b/parse.c
@@ -328,7 +328,7 @@ static AstDecl* parse_decl(Parser* p, bool is_param)
 
     if (!is_param && first->ty == AstDeclar_Function && p->curr.ty == '{') {
 
-        sema_function_enter(p->sema, declars[0]);
+        sema_function_enter(p->sema, spec, declars[0]);
         function_body = parse_stmt_block(p);
         sema_function_leave(p->sema);
 
diff --git a/sema.c b/sema.c
index 5ef46f6..38e352f 100644
--- a/sema.c
+++ b/sema.c
@@ -2,8 +2,68 @@
 #include "ast.h"
 #include "collection.h"
 #include <assert.h>
+#include <stddef.h>
+#include <stdio.h>
 #include <stdlib.h>
 
+static void type_spec_print(FILE* file, TypeSpec spec)
+{
+
+    struct {
+        TypeSpec spec;
+        const char* ident;
+    } spec_idents[] = {
+        { TypeSpec_Const, "const" },
+        { TypeSpec_Short, "short" },
+        { TypeSpec_Long, "long" },
+        { TypeSpec_Long2, "long" },
+        { TypeSpec_Unsigned, "unsigned" },
+    };
+
+    size_t spec_idents_size = sizeof(spec_idents) / sizeof(spec_idents[0]);
+
+    for (size_t i = 0; i < spec_idents_size; ++i) {
+        if (spec & spec_idents[i].spec) {
+            fprintf(file, "%s ", spec_idents[i].ident);
+        }
+    }
+}
+
+void type_print(FILE* file, const Type* type)
+{
+    type_spec_print(file, type->spec);
+
+    struct {
+        TypeTy ty;
+        const char* ident;
+    } ty_idents[] = {
+        { Type_Int, "int" },
+        { Type_Char, "char" },
+        { Type_Float, "float" },
+        { Type_Double, "double" },
+        { Type_Bool, "bool" },
+        { Type_Void, "void" },
+    };
+
+    size_t ty_idents_size = sizeof(ty_idents) / sizeof(ty_idents[0]);
+
+    for (size_t i = 0; i < ty_idents_size; ++i) {
+        if (type->ty == ty_idents[i].ty) {
+            fprintf(file, "%s", ty_idents[i].ident);
+            return;
+        }
+    }
+
+    if (type->ty == Type_Pointer) {
+        fprintf(file, " * ");
+        type_spec_print(file, type->pointer.spec);
+        type_print(file, type->pointer.inner);
+        return;
+    }
+
+    assert(false && "not implemented");
+}
+
 typedef struct {
     Hashmap ord_syms;
     Hashmap tag_syms;
@@ -27,8 +87,10 @@ static void rib_deinit(Rib* r)
 
 struct Sema {
     Arena sym_arena;
+    Arena type_arena;
     ARRAY_FIELD(Rib, ribs);
     Hashmap labels;
+    Keymap expr_types;
 };
 
 Sema* sema_new(void)
@@ -36,16 +98,20 @@ Sema* sema_new(void)
     Sema* s = malloc(sizeof(Sema));
     *s = (Sema) {
         .sym_arena = { },
+        .type_arena = { },
         ARRAY_FIELD_INIT(ribs),
         .labels = { },
+        .expr_types = { },
     };
 
     arena_init(&s->sym_arena, 1024);
+    arena_init(&s->type_arena, 1024);
 
     ARRAY_FIELD_PUSH(s, ribs, (&(Rib) { }));
     rib_init(&s->ribs[0]);
 
     hashmap_init(&s->labels, sizeof(LabelSym*));
+    keymap_init(&s->expr_types, sizeof(Type*));
 
     return s;
 }
@@ -53,11 +119,13 @@ Sema* sema_new(void)
 void sema_free(Sema* s)
 {
     arena_deinit(&s->sym_arena);
+    arena_deinit(&s->type_arena);
     for (size_t i = 0; i < s->ribs_size; ++i)
         rib_deinit(&s->ribs[i]);
     if (s->ribs)
         free(s->ribs);
     hashmap_deinit(&s->labels);
+    keymap_deinit(&s->expr_types);
     free(s);
 }
 
@@ -74,7 +142,162 @@ void sema_scope_leave(Sema* s)
     s->ribs_size -= 1;
 }
 
-void sema_function_enter(Sema* s, AstDeclar* declar)
+static Sym* get_ord_sym(Sema* s, const char* ident)
+{
+    Sym* sym = nullptr;
+    for (size_t i = 0; i < s->ribs_size; ++i)
+        if ((sym = hashmap_get(&s->ribs[s->ribs_size - i - 1].ord_syms, ident)))
+            break;
+    return sym;
+}
+
+static void error_if_multi_spec(
+    bool type_specced, Loc loc, const Type* first, TypeTy second_ty)
+{
+    if (type_specced) {
+        fprintf(stderr, "error: cannot combine type '");
+        type_print(stderr, &(Type) { .ty = second_ty });
+        fprintf(stderr, "' with type '");
+        type_print(stderr, first);
+        fprintf(stderr, "' on line %d\n", loc.line);
+        exit(1);
+    }
+}
+
+static void decode_decl_spec(Type* type, AstSpec as, Loc loc)
+{
+    bool type_specced = false;
+
+    if (as & AstSpec_Int) {
+        error_if_multi_spec(type_specced, loc, type, Type_Char);
+        type_specced = true;
+
+        type->ty = Type_Int;
+    }
+    if (as & AstSpec_Char) {
+        error_if_multi_spec(type_specced, loc, type, Type_Char);
+        type_specced = true;
+
+        type->ty = Type_Char;
+    }
+    if (as & AstSpec_Void) {
+        error_if_multi_spec(type_specced, loc, type, Type_Void);
+        type_specced = true;
+
+        type->ty = Type_Void;
+    }
+    if (as & (AstSpec_Enum | AstSpec_Struct | AstSpec_Union)) {
+        assert(false && "not implemented");
+    }
+
+    if (as & AstSpec_Unsigned) {
+        type->spec |= TypeSpec_Unsigned;
+    }
+    if (as & AstSpec_Const) {
+        type->spec |= TypeSpec_Const;
+    }
+}
+
+static Type* check_decl_type(Sema* s, AstDecl* decl)
+{
+    Type* type = arena_alloc(&s->type_arena, sizeof(Type));
+    *type = (Type) { };
+
+    decode_decl_spec(type, decl->spec, decl->loc);
+
+    return type;
+}
+
+static void error_if_redefinition(Hashmap* map, const char* ident, Loc loc)
+{
+    Sym* sym;
+    if ((sym = hashmap_get(map, ident))) {
+        fprintf(stderr,
+            "error: redefinition of '%s' on line %d\n",
+            ident,
+            loc.line);
+        exit(1);
+    }
+}
+
+static void check_declar(Sema* s,
+    AstDeclar* declar,
+    Type* type,
+    Type** out_declar_type,
+    const char** out_declar_ident)
+{
+    switch (declar->ty) {
+        case AstDeclar_Ident: {
+            *out_declar_type = type;
+            *out_declar_ident = declar->ident;
+            return;
+        }
+        case AstDeclar_Pointer: {
+            Type* new_type = arena_alloc(&s->type_arena, sizeof(Type));
+            *new_type = (Type) {
+                .ty = Type_Pointer,
+                .spec = 0,
+                .pointer = {
+                    .inner = type,
+                    .spec = 0,
+                },
+            };
+            decode_decl_spec(new_type, declar->pointer.spec, declar->loc);
+            check_declar(s,
+                declar->pointer.declar,
+                new_type,
+                out_declar_type,
+                out_declar_ident);
+            return;
+        }
+        case AstDeclar_Array: {
+            assert(false && "not implemented");
+            break;
+        }
+        case AstDeclar_Function: {
+            Type* new_type = arena_alloc(&s->type_arena, sizeof(Type));
+            *new_type = (Type) {
+                .ty = Type_Function,
+                .spec = 0,
+                .function = {
+                    .return_type = type,
+                    ARRAY_FIELD_INIT(params),
+                },
+            };
+
+            for (size_t i = 0; i < declar->function.params_size; ++i) {
+                AstDecl* param_decl = declar->function.params[i];
+
+                assert(param_decl->declars_size == 1);
+                AstDeclar* param_declar = param_decl->declars[0];
+
+                Type* decl_type = check_decl_type(s, param_decl);
+
+                const char* declar_ident;
+                Type* declar_type;
+                check_declar(
+                    s, param_declar, decl_type, &declar_type, &declar_ident);
+
+                (void)declar_ident;
+
+                ARENA_ARRAY_FIELD_PUSH(
+                    &s->type_arena, &new_type->function, params, &declar_type);
+            }
+
+            // TODO: handle forward declarations
+
+            check_declar(s,
+                declar->pointer.declar,
+                new_type,
+                out_declar_type,
+                out_declar_ident);
+            return;
+        }
+    }
+    assert(false && "unreachable");
+}
+
+void sema_function_enter(Sema* s, AstSpec spec, AstDeclar* declar)
 {
     assert(declar->ty == AstDeclar_Function);
 
@@ -82,9 +305,49 @@ void sema_function_enter(Sema* s, AstDeclar* declar)
     hashmap_deinit(&s->labels);
     hashmap_init(&s->labels, sizeof(LabelSym*));
 
+    Type* type = arena_alloc(&s->type_arena, sizeof(Type));
+    *type = (Type) { };
+    decode_decl_spec(type, spec, declar->loc);
+
+    Rib* rib = &s->ribs[s->ribs_size - 1];
+    error_if_redefinition(&rib->ord_syms, declar->ident, declar->loc);
+
+    Sym* sym = arena_alloc(&s->sym_arena, sizeof(Sym));
+    *sym = (Sym) {
+        .ty = Sym_Declar,
+        .declar = {
+            .type = type,
+        },
+    };
+    hashmap_set(&rib->ord_syms, declar->ident, &sym);
+
     sema_scope_enter(s);
 
-    for (size_t i = 0; i < declar->function.params_size; ++i) { }
+    for (size_t i = 0; i < declar->function.params_size; ++i) {
+        AstDecl* param_decl = declar->function.params[i];
+
+        assert(param_decl->declars_size == 1);
+        AstDeclar* param_declar = param_decl->declars[0];
+
+        Type* decl_type = check_decl_type(s, param_decl);
+
+        const char* declar_ident;
+        Type* declar_type;
+        check_declar(s, param_declar, decl_type, &declar_type, &declar_ident);
+
+        Rib* rib = &s->ribs[s->ribs_size - 1];
+        error_if_redefinition(&rib->ord_syms, declar->ident, declar->loc);
+
+        Sym* sym = arena_alloc(&s->sym_arena, sizeof(Sym));
+        *sym = (Sym) {
+            .ty = Sym_Param,
+            .param = {
+                .type = declar_type,
+                .idx = i,
+            },
+        };
+        hashmap_set(&rib->ord_syms, declar_ident, &sym);
+    }
 }
 
 void sema_function_leave(Sema* s)
@@ -92,15 +355,90 @@ void sema_function_leave(Sema* s)
     sema_scope_leave(s);
 }
 
-void sema_visit_function_declar(Sema* s, AstDeclar* declar)
-{
-}
-
 void sema_visit_stmt(Sema* s, AstStmt* stmt)
 {
-    if (stmt->ty == AstStmt_Decl) { }
+    if (stmt->ty == AstStmt_Decl) {
+        Type* type = check_decl_type(s, stmt->decl);
+
+        if (stmt->decl->function_body) {
+            // assume already handled
+            return;
+        }
+
+        for (size_t i = 0; i < stmt->decl->declars_size; ++i) {
+            AstDeclar* declar = stmt->decl->declars[i];
+
+            Type* declar_type;
+            const char* declar_ident;
+            check_declar(s, declar, type, &declar_type, &declar_ident);
+
+            Rib* rib = &s->ribs[s->ribs_size - 1];
+            error_if_redefinition(&rib->ord_syms, declar->ident, declar->loc);
+
+            Sym* sym = arena_alloc(&s->sym_arena, sizeof(Sym));
+            *sym = (Sym) {
+                .ty = Sym_Declar,
+                .declar = {
+                    .type = declar_type,
+                },
+            };
+            hashmap_set(&rib->ord_syms, declar_ident, &sym);
+        }
+    }
 }
 
 void sema_visit_expr(Sema* s, AstExpr* expr)
 {
+    Type* type = nullptr;
+
+    switch (expr->ty) {
+        case AstExpr_Ident: {
+            Sym* sym;
+            if ((sym = get_ord_sym(s, expr->ident)) == nullptr) {
+                fprintf(stderr,
+                    "error: undefined identifier '%s' on line %d\n",
+                    expr->ident,
+                    expr->loc.line);
+                exit(1);
+            }
+
+            switch (sym->ty) {
+                case Sym_Declar:
+                    type = sym->declar.type;
+                    break;
+                case Sym_Param:
+                    type = sym->param.type;
+                    break;
+            }
+
+            break;
+        }
+        case AstExpr_Str: {
+            Type* inner_type = arena_alloc(&s->type_arena, sizeof(Type));
+            *inner_type = (Type) {
+                .ty = Type_Char,
+                .spec = TypeSpec_Const,
+            };
+
+            type = arena_alloc(&s->type_arena, sizeof(Type));
+            *type = (Type) {
+                .ty = Type_Pointer,
+                .pointer = {
+                    .inner = inner_type,
+                    .spec = 0,
+                },
+            };
+            break;
+        };
+        case AstExpr_Call: {
+            Type* inner_type
+                = keymap_get(&s->expr_types, (size_t)expr->call.expr);
+            assert(inner_type);
+            printf("inner_type->ty == %d\n", inner_type->ty);
+            assert(inner_type->ty == Type_Function);
+            break;
+        }
+    }
+
+    keymap_set(&s->expr_types, (KeymapKey)expr, &type);
 }
diff --git a/sema.h b/sema.h
index f278eb0..c2ef09f 100644
--- a/sema.h
+++ b/sema.h
@@ -2,12 +2,65 @@
 #define SEMA_H
 
 #include "ast.h"
+#include "collection.h"
+#include <stddef.h>
+#include <stdio.h>
+
+typedef enum {
+    Type_None,
+    Type_Int,
+    Type_Char,
+    Type_Float,
+    Type_Double,
+    Type_Bool,
+    Type_Void,
+    Type_Pointer,
+    Type_Function,
+} TypeTy;
+
+typedef enum {
+    TypeSpec_Const = 1 << 0,
+    TypeSpec_Short = 1 << 1,
+    TypeSpec_Long = 1 << 2,
+    TypeSpec_Long2 = 1 << 3,
+    TypeSpec_Unsigned = 1 << 4,
+} TypeSpec;
+
+typedef struct Type Type;
+
+struct Type {
+    TypeTy ty;
+    TypeSpec spec;
+    union {
+        struct {
+            Type* inner;
+            TypeSpec spec;
+        } pointer;
+        struct {
+            Type* return_type;
+            ARRAY_FIELD(Type*, params);
+        } function;
+    };
+};
+
+void type_print(FILE* file, const Type* type);
+
 typedef enum {
     Sym_Declar,
+    Sym_Param,
 } SymTy;
 
 typedef struct {
     SymTy ty;
+    union {
+        struct {
+            Type* type;
+        } declar;
+        struct {
+            Type* type;
+            size_t idx;
+        } param;
+    };
 } Sym;
 
 typedef struct {
@@ -22,7 +75,7 @@ void sema_free(Sema* s);
 void sema_scope_enter(Sema* s);
 void sema_scope_leave(Sema* s);
 
-void sema_function_enter(Sema* s, AstDeclar* declar);
+void sema_function_enter(Sema* s, AstSpec spec, AstDeclar* declar);
 void sema_function_leave(Sema* s);
 
 void sema_visit_stmt(Sema* s, AstStmt* stmt);