compiler-construction – Page 28

What kinds of patterns could I enforce on the code to make it easier to translate to another programming language? [closed]

January 14, 2023 by Tarik

I’ve been building tools (DMS Software Reengineering Toolkit) to do general purpose program manipulation (with language translation being a special case) since 1995, supported by a strong team of computer scientists. DMS provides generic parsing, AST building, symbol tables, control and data flow analysis, application of translation rules, regeneration of source text with comments, etc., … Read more

Are GCC and Clang parsers really handwritten?

January 9, 2023 by Tarik

There’s a folk-theorem that says C is hard to parse, and C++ essentially impossible. It isn’t true. What is true is that C and C++ are pretty hard to parse using LALR(1) parsers without hacking the parsing machinery and tangling in symbol table data. GCC in fact used to parse them, using YACC and additional … Read more

Why does this (null || !TryParse) conditional result in “use of unassigned local variable”?

January 8, 2023 by Tarik

I am pretty sure this is a compiler bug. Nice find! Edit: it is not a bug, as Quartermeister demonstrates; dynamic might implement a weird true operator which might cause y to never be initialized. Here’s a minimal repro: class Program { static bool M(out int x) { x = 123; return true; } static … Read more

How is -march different from -mtune?

January 8, 2023 by Tarik

If you use -march then GCC will be free to generate instructions that work on the specified CPU, but (typically) not on earlier CPUs in the architecture family. If you just use -mtune, then the compiler will generate code that works on any of them, but will favour instruction sequences that run fastest on the … Read more

How to approach creating a JVM programming language?

January 8, 2023 by Tarik

I would also recommend ASM, but have a look at Jasmin, I used it (or, rather, had to use it) for a university project, and it worked quite well. I wrote a lexer-parser-analyzer-optimizer-generator combination for a programing language using Java and Jasmin, so it was generating JVM Code. I uploaded the code here; the interesting … Read more

implementing type inference

January 7, 2023 by Tarik

I found the following resources helpful for understanding type inference, in order of increasing difficulty: Chapter 30 (Type Inference) of the freely available book PLAI, Programming Languages: Application and Interpretation, sketches unification-based type inference. The summer course Interpreting types as abstract values presents elegant evaluators, type checkers, type reconstructors and inferencers using Haskell as a … Read more

Is gcc C compiler written in C itself?

January 7, 2023 by Tarik

The specific history to gcc is given at the GCC Wiki. The more general point is that compilers are generally originally compiled with some other compiler until they are powerful enough to compile themselves. Alternately, it is possible to write a basic compiler that can handle a subset of your features in assembler, and build … Read more

Bootstrapping still requires outside support

January 3, 2023 by Tarik

Is there a way to actually write a compiler in its own language? You have to have some existing language to write your new compiler in. If you were writing a new, say, C++ compiler, you would just write it in C++ and compile it with an existing compiler first. On the other hand, if … Read more

Why is it impossible to build a compiler that can determine if a C++ function will change the value of a particular variable?

January 2, 2023 by Tarik

Why is it impossible to build such a compiler? For the same reason that you can’t write a program that will determine whether any given program will terminate. This is known as the halting problem, and it’s one of those things that’s not computable. To be clear, you can write a compiler that can determine … Read more

Eclipse: enable assertions

January 1, 2023 by Tarik

Go to the menu Run, and then to the menu item Run Configurations. In the left panel, go to Java Application, and then go to Assertions. In the right panel, choose the tab Arguments. Under the field for VM arguments, type -ea to enable assertions. Click on the Apply and then Run button. To globally … Read more