95
votes
Detect manual changes to an autogenerated C header
I think you are approaching this problem from the wrong angle.
Better let the generator place a clear and visible comment at the beginning of the C header file like
// This file is autogenerated, ...
- 221k
54
votes
Do compilers optimise in concurrency?
Asuming expensive_calc_one and expensive_calc_two are pure functions
Unfortunately, determining whether a function is pure is equivalent to solving the Halting Problem in the general case. So, you ...
- 105k
41
votes
Detect manual changes to an autogenerated C header
Don't commit the generated C header file at all. In fact, delete the current file (thanks @user1936), change the script to call the header file .g.h (thanks @davidbak),
and add it to .gitignore, so ...
- 565
37
votes
Accepted
How do compilers work in a language that doesn't allow recursion?
Recursion can only be programmed either by having a call to function A within the definition of A itself (direct), or by having function A call function B, and function B call function A (indirect). ...
- 111k
37
votes
Why is it necessary to mark classes as not inherited from? Can't an optimizer automatically detect that virtual calls are unnecessary?
Don't we need to take a step back here?
Under the hood, it generally all boils down to simply functions being called the with the this pointer as first arg.
It's good to question things from first ...
- 5,205
27
votes
How do compilers work in a language that doesn't allow recursion?
To support recursion, a language needs to support function calls and a call stack. When a language doesn't allow recursion, it's typically because the language lacks one of these features. I'm not ...
- 62.4k
21
votes
How can we avoid showing the literal path in the exception's stack trace?
Couple of pointers.
You should never expose stacktrace to users. Thats a security risk. You should also never expose exception messages to users, only for custom exceptions that you know can not ...
- 671
17
votes
Detect manual changes to an autogenerated C header
First a disclaimer: I don't think this is a good idea.
But here is one way to do it anyway:
void check_file_time() {
if (strcmp(__TIMESTAMP__, "Sun Feb 16 19:38:35 2020") != 0)
{
asm(...
- 1,406
15
votes
Accepted
Is there any use case for using 'L' letter after a number literal in C?
In the C language expressions are typed inside-out: literals have types. E.g. 123 is an int, and 123U is an unsigned int, 123L is a long int and so on. The type of an expression depends on the types ...
- 136k
15
votes
Accepted
What are the 'practical' advantages of LR parser over LL parser 'in today'?
True LL parsers are fast and simple – but also completely unable to parse many interesting languages. Many real-world programming languages are in the LALR class, which is closely related to LR but ...
- 136k
15
votes
How does code work without getting compiled or interpreted?
Compilers aren't magic - they're just programs, which can be run from the command line. Visual Studio Code has a "Terminal" tab in the bottom pane of the default UI, where you can invoke the ...
- 880
14
votes
Why C allows multiple global declarations of the same variable but NOT multiple local declarations?
@msc gives a good introduction into the rules behind this behavior.
I noticed that if I declare a global variable multiple times the compiler does not even output a warning.
C has three kinds of ...
- 34.8k
13
votes
Accepted
Why does Forth's flexibility make a grammar inappropriate for it?
A "normal" word is pretty much just a subroutine.
...but you can write a user-defined defining word, which change how the compiler works. For example, a definition normally starts with a colon (":") ...
- 44.9k
13
votes
Difference between direct and indirect function() calls
The main difference between the direct and the indirect call, is that:
the direct call uses an instruction call with a fixed address as argument. After the linker has done its job, this address will ...
- 82.3k
12
votes
Accepted
In c++, is there a way inside a function block, to execute cleanup code after the value has been returned?
Addressing the question about cleanup code:
yes, there is a way,
it's called RAII (for Resource Acquisition Is Initialization, an acronym whose limpid clarity is rivalled only by CRTP), and
it is both ...
- 12.9k
12
votes
Why is it necessary to mark classes as not inherited from? Can't an optimizer automatically detect that virtual calls are unnecessary?
Imagine this extremely simple example
A value = Random.Shared.Next(0, 2) == 0 ? new B() : new C();
value.M();
abstract class A
{
public abstract void M();
}
class B : A
{
public override ...
- 38.2k
11
votes
Why C allows multiple global declarations of the same variable but NOT multiple local declarations?
According to coding-guidelines :
In the set of translation units and libraries that constitutes an
entire program, each declaration of a particular identifier with
external linkage denotes the ...
- 307
11
votes
Accepted
How to make compiler portable?
You cannot make a portable compiler (not in the sense you dream of).
You could make a compiler for a particular target machine -or language- (and that machine might even be something like LLVM or ...
- 32.9k
11
votes
Accepted
Only one number type in language design
We have different number representation in general because they have different strengths and weaknesses, be it speed, precision, or range. Also this has to be the case because we cannot represent all ...
- 10.3k
11
votes
Accepted
Should my lexer allow what is obviously a syntax error?
Your lexer is never going to be able to diagnose all syntax errors unless you make it as powerful as the parser itself. This would be a large and totally unnecessary amount of work, and the only ...
- 111k
10
votes
Accepted
Does the Perfect Compiler trump source differences
No:
First, let's note that there are many, many equivalent yet differing code sequences when it comes to machine code (let alone other languages). A simple case is swapping two registers where ...
- 34.8k
10
votes
How to optimize a mixed stack/register bytecode with control flow and side effects?
There's a huge body of research on this topic, so I really recommend reading a compiler book. Muchnik's book can work well as a reference. I really like Modern Compiler Implementation but I think it's ...
- 301
10
votes
How can one interpret an Abstract Syntax Tree without recursion?
You can systematically calculate such an approach. For simplicity, I'll consider evaluating arithmetic expressions, but the transforms are completely mechanical. I'll use Haskell as the language.
data ...
- 6,831
10
votes
How can we avoid showing the literal path in the exception's stack trace?
From this blog:
<PropertyGroup>
<PathMap>$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)'))=./</PathMap>
</PropertyGroup>
So instead of this:
Unhandled ...
- 241
10
votes
Accepted
code generation - would C be a good compiler backend?
Define "good" and "bad" backend
According to what criteria do you evaluate whether it is a good or bad solution? Without knowing, we are more in subjective beliefs rather than objective advise:
...
- 82.3k
10
votes
Accepted
In C++, If a member function can be made static with no change to functionality, are there any performance or memory benefits from doing so?
Practically in 99.9% of cases: no.
Theoretically: maybe. You won't be passing the implicit this parameter to every function, and not passing that could save you bytes and the time passing those bytes. ...
- 26.1k
10
votes
Is it possible to make a compiler for any dynamic/script/interpreter language
Can we (Is it possible to) make a compiler for any dynamic/script/interpreter language,
Yes, it is.
Note that there is no such thing as an "interpreter" language. An interpreter is a ...
- 105k
9
votes
Accepted
Why am I advised to not inline functions that are called only once?
In C and C++, the inline keyword has effects that make inline possible, but also many other effects – such as suppressing the one-definition rule (ODR). This can obscure bugs.
Therefore, the inline ...
- 136k
9
votes
Accepted
How does a compiler work when it's not directly compiling to machine code
I know the compilation process goes with this flow:
source -> parse -> AST -> intermediate code -> assembly -> machine code
,and in the case of Java you will have bytecode which ...
- 105k
9
votes
Accepted
Relationship between the C standard libraries and Java standard libraries
Which is the relationship between the standard libraries of C language and the standard libraries of other software platforms, e.g. Java, .NET, Python?
There is no relationship.
Some library ...
- 105k
Only top scored, non community-wiki answers of a minimum length are eligible