Compile vararg

README.md

@@ -0,0 +1,59 @@
+# Simple C-compiler
+
+This is a simple work-in-progress C-compiler (or C-like) written in C++ with the
+goal of learning to write C++ better in the future, and to provide reference for
+my knowledge about modern C++ programming.
+
+As of writing, a simple fibonacci sequence program is already possible to be
+compiled and executed, and can be viewed via [`test.c`](./test.c).
+
+As far as compiler-design goes, this project still falls behind my other
+project, [Reid-LLVM](https://git.teascade.net/teascade/reid-llvm), which is
+significantly more capable and more robust.
+
+## Structure of the program
+
+The program is structured into several different staged, all of which are
+orchestrated via main.cpp.
+
+Currently the stages are as follows:
+
+1. Firstly, the program is **tokenized**. This stage could also be called the
+   lexer, depending on your preference. In this stage, the source code for the
+   program is transformed into discrete tokens which can then be used during the
+   parsing phase easier than regular text. The code for this stage is mostly in
+   [`src/tokens.cpp`](src/tokens.cpp).
+2. **TODO:** Preprocessing stage hasn't yet been developed, but it will go here.
+3. Then the program is **parsed**. This is the stage where the tokens from the
+   previous stage(s) are converted into an Abstract Syntax Tree (AST), which is
+   a format that is easier for the computer to process. The AST itself lives in
+   [`src/ast.h`](src/ast.h), and the code for the parsing phase lives in
+   [`src/parsing.cpp`](src/parsing.cpp).
+4. **TODO:** Typechecking phase hasn't yet been developed, but it will go here.
+5. Finally the program is **compiled**, or in other words **code-generated**,
+   hence why this is the **codegen** stage. This is where the AST from the
+   previous stages is taken and LLVM Intermediate Representation is produced
+   using LLVM-bindings. 
+
+## Compiling and running the program
+
+In order to compile the program, you need the following:
+- CMake
+- C++20 (or newer) capable compiler
+- LLVM 21.1.0 or newer
+
+And in order to execute the program which is compiled you also need:
+- LLVM 21.1.0 or newer (as it is dynamically linked)
+- `whereis`-utility in `$PATH`
+- `ld`-utility in `$PATH`
+
+Then, to compile the program you run:
+```sh
+cmake -Bbuild
+make -C build
+```
+
+and to run the program, run simply `./build/llvm_c_compiler`. This will read a
+file called `test.c` from `$PWD`, and produce two files (`test.o` and `test`).
+An executable file called `test` is produced as a result, compiled from the
+original `test.c`.

src/ast.cpp

@@ -9,6 +9,12 @@ namespace AST {
         return out.str();
     }
 
+    std::string StringLiteralExpression::formatted() {
+        std::stringstream out{ "" };
+        out << "\"" << this->m_value << "\"";
+        return out.str();
+    }
+
     std::string ValueReferenceExpression::formatted() {
         return this->m_name;
     }
@@ -80,17 +86,26 @@ namespace AST {
         for (auto& param : this->m_params) {
             if (counter++ > 0)
                 out << ", ";
-            out << param.second->formatted() << " " << param.first;
+            out << param.second->formatted();
+            if (param.first) {
+                out << " " << *param.first;
+            }
+        }
+        if (this->m_is_vararg) {
+            if (counter > 0)
+                out << ", ";
+            out << "...";
         }
 
         out << ") -> ";
         out << this->m_return_ty->formatted();
-        out << " {\n";
-        for (auto& statement : this->m_statements) {
-            out << "  " << statement->formatted() << "\n";
+        if (this->m_statements) {
+            out << " {\n";
+            for (auto& statement : *this->m_statements) {
+                out << "  " << statement->formatted() << "\n";
+            }
+            out << "}";
         }
-
-        out << "}";
         return out.str();
     }
 }

src/ast.h

@@ -41,6 +41,16 @@ namespace AST {
         virtual codegen::StackValue codegen(codegen::Builder& builder, codegen::Scope& scope) override;
     };
 
+    class StringLiteralExpression : public Expression {
+    private:
+        std::string m_value;
+    public:
+        StringLiteralExpression(token::Metadata meta, std::string value) : Expression{ meta }, m_value{ value } {}
+        virtual ~StringLiteralExpression() override = default;
+        virtual std::string formatted() override;
+        virtual codegen::StackValue codegen(codegen::Builder& builder, codegen::Scope& scope) override;
+    };
+
     class ValueReferenceExpression : public Expression {
     private:
         std::string m_name;
@@ -165,19 +175,22 @@ namespace AST {
     class Function : public TopLevelStatement {
     private:
         std::unique_ptr<types::Type> m_return_ty;
-        std::vector<std::pair<std::string, std::unique_ptr<types::Type>>> m_params;
+        std::vector<std::pair<std::optional<std::string>, std::unique_ptr<types::Type>>> m_params;
+        bool m_is_vararg;
         std::string m_name;
-        std::vector<std::unique_ptr<Statement>> m_statements;
+        std::optional<std::vector<std::unique_ptr<Statement>>> m_statements;
     public:
         Function(
             token::Metadata meta,
             std::unique_ptr<types::Type> return_ty,
-            std::vector<std::pair<std::string, std::unique_ptr<types::Type>>> params,
+            std::vector<std::pair<std::optional<std::string>, std::unique_ptr<types::Type>>> params,
+            bool is_vararg,
             std::string name,
-            std::vector<std::unique_ptr<Statement>> statements)
+            std::optional<std::vector<std::unique_ptr<Statement>>> statements)
             : TopLevelStatement{ meta }
             , m_return_ty{ std::move(return_ty) }
             , m_params{ std::move(params) }
+            , m_is_vararg{ is_vararg }
             , m_name{ name }
             , m_statements{ std::move(statements) } {
         }

src/codegen.cpp

@@ -22,7 +22,19 @@ namespace AST {
 
         return codegen::StackValue{
             llvm::ConstantInt::get(ty, this->m_value),
-             std::unique_ptr<types::Type>{stack_type}
+            std::unique_ptr<types::Type>{stack_type}
+        };
+    }
+
+    codegen::StackValue StringLiteralExpression::codegen(codegen::Builder& builder, codegen::Scope&) {
+
+        auto stack_type = new types::PointerType{ std::make_unique<types::FundamentalType>(types::FundamentalTypeKind::Char) };
+
+        auto str = llvm::StringRef{ this->m_value.c_str() };
+
+        return codegen::StackValue{
+            builder.builder->CreateGlobalString(str),
+            std::unique_ptr<types::Type>{stack_type},
         };
     }
 
@@ -175,7 +187,7 @@ namespace AST {
             param_ty_ptrs.push_back(std::move(param.second));
         }
 
-        auto fn_ty_ptr = std::shared_ptr<types::Type>{ new types::FunctionType{ ret_ty_ptr, param_ty_ptrs } };
+        auto fn_ty_ptr = std::shared_ptr<types::Type>{ new types::FunctionType{ ret_ty_ptr, param_ty_ptrs, this->m_is_vararg } };
 
         auto fn_ty = fn_ty_ptr->codegen(builder);
         auto function = llvm::Function::Create(
@@ -187,24 +199,28 @@ namespace AST {
 
         scope.values[this->m_name] = codegen::StackValue{ function, fn_ty_ptr };
 
-        auto BB = llvm::BasicBlock::Create(*builder.context, "entry", function, nullptr);
-        builder.block = BB;
+        if (this->m_statements) {
+            auto BB = llvm::BasicBlock::Create(*builder.context, "entry", function, nullptr);
+            builder.block = BB;
 
-        codegen::Scope inner_scope{ scope };
+            codegen::Scope inner_scope{ scope };
 
-        int counter = 0;
-        for (auto& param : this->m_params) {
-            auto param_ty_ptr = param_ty_ptrs[counter];
-            auto arg = function->getArg(counter++);
-            arg->setName(param.first);
-            inner_scope.values[param.first] = codegen::StackValue{
-                arg,
-                param_ty_ptr,
-            };
-        }
+            int counter = 0;
+            for (auto& param : this->m_params) {
+                auto param_ty_ptr = param_ty_ptrs[counter];
+                auto arg = function->getArg(counter++);
+                if (param.first) {
+                    arg->setName(*param.first);
+                    inner_scope.values[*param.first] = codegen::StackValue{
+                        arg,
+                        param_ty_ptr,
+                    };
+                }
+            }
 
-        for (auto& statement : this->m_statements) {
-            statement->codegen(builder, inner_scope);
+            for (auto& statement : *this->m_statements) {
+                statement->codegen(builder, inner_scope);
+            }
         }
 
         llvm::verifyFunction(*function);
@@ -220,6 +236,10 @@ namespace types {
             return builder.builder->getInt32Ty();
         case FundamentalTypeKind::Bool:
             return builder.builder->getInt1Ty();
+        case FundamentalTypeKind::Char:
+            return builder.builder->getInt8Ty();
+        case FundamentalTypeKind::Void:
+            return builder.builder->getVoidTy();
         default:
             return builder.builder->getVoidTy();
         }
@@ -234,7 +254,7 @@ namespace types {
 
         auto ret_ty = this->m_ret_ty->codegen(builder);
 
-        return llvm::FunctionType::get(ret_ty, params, false);
+        return llvm::FunctionType::get(ret_ty, params, this->m_vararg);
     }
 
     llvm::Type* PointerType::codegen(codegen::Builder& builder) {

src/main.cpp

@@ -20,8 +20,6 @@
 #include "tokens.h"
 #include "parsing.h"
 
-void llvm_hello_world();
-
 std::string read_file(std::string_view filepath) {
     std::ifstream input{ std::string{filepath} };
     if (!input) {
@@ -161,11 +159,18 @@ std::optional<CompileOutput> compile(std::string_view in_filename) {
     };
 }
 
+struct ClosePipeDeleter {
+    // Note 2: Consider adding noexcept.
+    void operator()(FILE* file) const {
+        pclose(file);
+    }
+};
+
 /// @brief Executes a given command and returns the output as std::string
 std::string exec(const char* cmd) {
     std::array<char, 128> buffer;
     std::string result;
-    std::unique_ptr<FILE, decltype(&pclose)> pipe(popen(cmd, "r"), pclose);
+    std::unique_ptr<FILE, ClosePipeDeleter> pipe(popen(cmd, "r"), ClosePipeDeleter{});
     if (!pipe) {
         throw std::runtime_error("popen() failed!");
     }

src/parsing.cpp

@@ -12,10 +12,37 @@ namespace parsing {
             try {
                 auto token = inner.expect(token::Type::Ident);
 
+                // TODO eventually make this be potentially more than one word
+                std::string type_name = token.content;
+
+                std::unique_ptr<types::Type> returned{};
+
+                if (type_name == "int") {
+                    auto ty = new types::FundamentalType{ types::FundamentalTypeKind::Int };
+                    returned = std::unique_ptr<types::Type>{ ty };
+                }
+                else if (type_name == "char") {
+                    auto ty = new types::FundamentalType{ types::FundamentalTypeKind::Char };
+                    returned = std::unique_ptr<types::Type>{ ty };
+                }
+                else if (type_name == "void") {
+                    auto ty = new types::FundamentalType{ types::FundamentalTypeKind::Void };
+                    returned = std::unique_ptr<types::Type>{ ty };
+                }
+                else {
+                    throw std::runtime_error("Expected type name, got " + type_name);
+                }
+
+                while (inner.peek().type == token::Type::Symbol && inner.peek().content == "*") {
+                    inner.next();
+                    auto ty = new types::PointerType{ std::move(returned) };
+                    returned = std::unique_ptr<types::Type>{ ty };
+                }
+
+
                 stream.m_position = inner.m_position;
 
-                auto ty = new types::FundamentalType{ types::FundamentalTypeKind::Int };
-                return std::unique_ptr<types::Type>{ ty };
+                return returned;
             }
             catch (std::runtime_error& error) {
                 return std::string{ error.what() };
@@ -32,6 +59,12 @@ namespace parsing {
                     auto expr = new AST::IntLiteralExpression{ token.metadata, std::stoi(token.content) };
                     return std::unique_ptr<AST::Expression>{ expr };
                 }
+                else if (token.type == token::Type::LiteralStr) {
+                    stream.m_position = inner.m_position;
+
+                    auto expr = new AST::StringLiteralExpression{ token.metadata, token.content };
+                    return std::unique_ptr<AST::Expression>{ expr };
+                }
                 else if (token.type == token::Type::Ident) {
                     stream.m_position = inner.m_position;
 
@@ -241,33 +274,60 @@ namespace parsing {
             auto name_token = inner.expect(token::Type::Ident);
             inner.expect(token::Type::Symbol, "(");
 
-            std::vector<std::pair<std::string, std::unique_ptr<types::Type>>> params;
+            std::vector<std::pair<std::optional<std::string>, std::unique_ptr<types::Type>>> params;
+            bool is_vararg = false;
             while (inner.peek().content != ")") {
                 if (params.size() > 0) {
                     inner.expect(token::Type::Symbol, ",");
                 }
+
+                if (inner.peek().content == ".") {
+                    inner.next();
+                    inner.expect(token::Type::Symbol, ".");
+                    inner.expect(token::Type::Symbol, ".");
+                    is_vararg = true;
+                    break;
+                }
+
                 auto param_ty = parse_type(inner).unwrap();
-                auto param_name = inner.expect(token::Type::Ident);
-                params.push_back(std::pair(param_name.content, std::move(param_ty)));
+                std::optional<std::string> param_name{};
+                if (inner.peek().type == token::Type::Ident) {
+                    param_name = inner.expect(token::Type::Ident).content;
+                }
+                params.push_back(std::pair(param_name, std::move(param_ty)));
             }
 
             inner.expect(token::Type::Symbol, ")");
-            inner.expect(token::Type::Symbol, "{");
 
-            std::vector<std::unique_ptr<AST::Statement>> statements{};
+            std::optional<std::vector<std::unique_ptr<AST::Statement>>> statements{};
+            if (inner.peek().content == "{") {
+                inner.expect(token::Type::Symbol, "{");
 
-            auto statement = parse_statement(inner);
-            while (statement.ok()) {
-                statements.push_back(statement.unwrap());
-                statement = parse_statement(inner);
+                std::vector<std::unique_ptr<AST::Statement>> statement_list{};
+
+                auto statement = parse_statement(inner);
+                while (statement.ok()) {
+                    statement_list.push_back(statement.unwrap());
+                    statement = parse_statement(inner);
+                }
+
+                statements = std::optional{ std::move(statement_list) };
+                inner.expect(token::Type::Symbol, "}");
+            }
+            else {
+                inner.expect(token::Type::Symbol, ";");
             }
-
-
-            inner.expect(token::Type::Symbol, "}");
 
             stream.m_position = inner.m_position;
 
-            auto fun = new AST::Function{ before_meta + stream.metadata(), std::move(type), std::move(params), name_token.content, std::move(statements) };
+            auto fun = new AST::Function{
+                before_meta + stream.metadata(),
+                std::move(type),
+                std::move(params),
+                is_vararg,
+                name_token.content,
+                std::move(statements)
+            };
             return std::unique_ptr<AST::TopLevelStatement>{ fun };
         }
         catch (std::runtime_error& error) {

src/tokens.cpp

@@ -23,6 +23,8 @@ namespace token {
             return "Symbol";
         case token::Type::LiteralInt:
             return "LiteralInt";
+        case token::Type::LiteralStr:
+            return "LiteralStr";
 
         case token::Type::ReturnKeyword:
             return "Return";
@@ -126,7 +128,9 @@ namespace token {
         uint32_t line = 0;
         uint32_t line_start = 0;
 
-        for (int i = 0; i < static_cast<int>(text.length());) {
+        int text_length = static_cast<int>(text.length());
+
+        for (int i = 0; i < text_length;) {
             Position position{ line, i - line_start };
             Metadata meta{ position, position, filename };
 
@@ -136,14 +140,27 @@ namespace token {
                 std::string content{};
                 do {
                     content += c;
+                    if ((i + 1) >= text_length) break;
                     c = text[++i];
                 } while (std::isdigit(c));
                 tokens.push_back(token::Token{ token::Type::LiteralInt, content, meta + content.size() });
             }
+            else if (c == '\"') {
+                std::string content{};
+                c = text[++i]; // Skip initial "
+                do {
+                    content += c;
+                    if ((i + 1) >= text_length) break;
+                    c = text[++i];
+                } while (c != '\"');
+                i++; // Skip second "
+                tokens.push_back(token::Token{ token::Type::LiteralStr, content, meta + (content.size() + 2) });
+            }
             else if (std::isalpha(c)) {
                 std::string content{};
                 do {
                     content += c;
+                    if ((i + 1) >= text_length) break;
                     c = text[++i];
                 } while (std::isalnum(c));
 
@@ -167,6 +184,7 @@ namespace token {
                         line_start = i + 1;
                     }
                     content += c;
+                    if ((i + 1) >= text_length) break;
                     c = text[++i];
                 } while (iswhitespace(c));
                 // tokens.push_back(token::Token{ token::Type::Whitespace, content });

src/tokens.h

@@ -11,6 +11,7 @@ namespace token {
         Ident,
         Symbol,
         LiteralInt,
+        LiteralStr,
 
         ReturnKeyword,
         IfKeyword,

src/types.cpp

@@ -42,6 +42,12 @@ namespace types {
         switch (this->m_ty) {
         case FundamentalTypeKind::Int:
             return "Int";
+        case FundamentalTypeKind::Bool:
+            return "Bool";
+        case FundamentalTypeKind::Char:
+            return "Char";
+        case FundamentalTypeKind::Void:
+            return "Void";
         default:
             return "Unknown";
         }
@@ -103,6 +109,12 @@ namespace types {
             out << param->formatted();
         }
 
+        if (this->m_vararg) {
+            if (counter > 0)
+                out << ", ";
+            out << "...";
+        }
+
         out << ") -> " << this->m_ret_ty->formatted();
         return out.str();
     }
@@ -134,7 +146,7 @@ namespace types {
 
     std::string PointerType::formatted() {
         std::stringstream out{ "" };
-        out << this->m_inner << "*";
+        out << this->m_inner->formatted() << "*";
         return out.str();
     }
 

src/types.h

@@ -20,7 +20,9 @@ namespace types {
 
     enum FundamentalTypeKind {
         Int,
-        Bool
+        Bool,
+        Char,
+        Void,
     };
 
     class Type {
@@ -57,9 +59,10 @@ namespace types {
     private:
         std::shared_ptr<Type> m_ret_ty;
         std::vector<std::shared_ptr<Type>> m_param_tys;
+        bool m_vararg;
     public:
-        FunctionType(std::shared_ptr<Type> ret_ty, std::vector<std::shared_ptr<Type>> param_tys)
-            : m_ret_ty{ std::move(ret_ty) }, m_param_tys{ std::move(param_tys) } {
+        FunctionType(std::shared_ptr<Type> ret_ty, std::vector<std::shared_ptr<Type>> param_tys, bool vararg)
+            : m_ret_ty{ std::move(ret_ty) }, m_param_tys{ std::move(param_tys) }, m_vararg{ vararg } {
         }
         virtual ~FunctionType() override = default;
         virtual std::string formatted() override;

test.c

@@ -1,3 +1,5 @@
+void printf(char*, ...);
+
 int fibonacci(int n) {
     if (n < 2)
         return 1;
@@ -5,5 +7,6 @@ int fibonacci(int n) {
 }
 
 int main() {
-    return fibonacci(10);
+    printf("10th fibonacci number is %d!", fibonacci(10));
+    return 0;
 }