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In Git documentation, there are lots of references to the term "HEAD". But what exactly is it? Some places refer to it as "a pointer to the current branch". So it's a branch? What is it used for?
What exactly must a C compiler do when it finds a compile-time error? The most obvious kind of errors are language syntax errors, but the C standard also speaks of constraints, which are rules tha...
To protect against dictionary and rainbow table attacks it is well known that passwords should be salted before hashing. The salt (unique to each password) gets stored with the hash, often in the s...
When writing Python-based apps (e.g. Django, Flask, etc.), it's often the case that import statements can be found all over the place, often more than once for the same module. For example, you can...
I often see the construct if __name__ == '__main__' in Python code. For example, the queens.py demo in the Python repository ends with these two lines: if __name__ == "__main__": main() Ho...
We have two teams, dev and doc, and I'd like them to have shared access (via git) to a common subset of content. Specifically, I would like the examples that are used in the doc and that are scrip...
The following list comprehension worked when I tried it: [num for num in hand if num != 11] But this doesn't work: [num for num in hand if num != 11 else 22] It gives a SyntaxError, highlightin...
I heard rumours that the strcpy function is dangerous and shouldn't be used. Supposedly it can be exploited to create buffer overflows somehow. And indeed when I compile my C code in the admittedl...
I have a small new Python 3.8 Flask project with some relative import quirks. For the DB I use SQLAlchemy with Flask-Migrate. My project has the following general structure: controllers/ static/ te...
Let's say I have a script that needs the user to set X number of variables at the start. One can either Pass the arguments in on the command line. Start the program and then have the user input...
When I have tried to read technical explanations of the syntax rules for programming languages, and when I am trying to decipher error messages, I often encounter the terms expression and statement...
When reading questions about C programming from beginners, I very often see them describing peculiar run-time errors and crashes, segmentation faults and similar. They have spent a lot of time chas...
I spend a lot of time writing CLI tools in Python, and I would like to support tab-completion in a style similar to Git. For example, subcommands should be tab-completable, options should expand ba...
Lets say I have two tables, A and B and I need to join a subset of them. Is there best practices of sticking the conditions in the WHERE clause like this, SELECT * FROM A JOIN B on a.fk_b = b....
Tldr; I don't need to parse HTML, but I need to check if user submitted input conforms to a very strict subset of HTML. Can regex be a suitable tool for this? Details I have a frontend sanitiser th...
I have created this sensational program: #include <stdio.h> int* func (void) { int local=5; return &local; } int main (void) { printf("%d\n", *func()); } This prints 5 even thoug...
I'm working on an API to respond some data about a bunch of orders and items. The order and item numbers are always an integer (it's the order.id and item.id value, respectively). Originally the re...
Consider the following method as an example: List<int> Foo() { // ... } Are there any disadvantages of returning an interface instead of a concrete implementation in C#? IList<i...
How do I clone the repository with only part of the history? For example, let's say I want to download only the last 5 commits out of thousands.
What exactly does the static keyword do in C? I have seen it used in several diverse contexts: 1) As a variable outside a function: #include <stdio.h> static int x = 5; int main (void) ...
I recently told a friend that malloc(n) allocates and returns a pointer to a block of at least N bytes of memory, as opposed to exactly N; that it is allowed to allocate 'extra' memory to meet e.g....
I'm using an object-oriented design for my C project and trying to implement classes with private encapsulation. How do I do this? Some things I've tried that are problematic: Using a struct f...
When writing any form of custom function such as this: void func (int* a, int* b) Should I add code to check if a and b are null pointers or not? if(a == NULL) /* error handling */ When po...
Using Vim, I am trying to search for all instances of a specific string, except for those that fall somewhere in between two other specific strings. For example, I want to determine all instances ...
I am developing an application that targets Linux-based OS, and I need to store the user's configuration, metadata and other things in a persistent way (i.e. on the file system). I know that one c...
Is it correct to destroy a mutex which is referenced but not owned by an unique_lock as in this code? { std::unique_ptr<std::mutex> mutex = std::make_unique<std::mutex>(); std::u...
tl;dr I'd like to learn a compact, cross-compiler way of selectively suppressing compiler warnings. Consider the case where you really mean to make an exact floating-point comparison using ==, o...
I've seen some regular expressions (regex) using \s when they want to match a space, but I noticed that it also matches line breaks. Example: the regex [a-z]\s[0-9] (lowercase ASCII letter, follow...
I have a large and complex PostgreSQL SELECT query that I would like to make faster. EXPLAIN suggests it should run quickly, with the worst parts being scans of a few thousand rows. When run, it do...
The C language has gone through many iterations and the latest one not yet released is informally called "C23", supposedly because they hoped to release it in 2023. The latest draft version N3096 i...
I have seen this construct quite a lot: int *p = (int*) malloc(n * sizeof(int)); Is this how it should be? What is the proper way to use malloc? I have also seen this: int *p = malloc(n * size...
Consider the following code: #include <stdio.h> int main() { int a = 5; int b; ++*(&b + 1); printf("%d\n", a); return 0; } The output is as expected: 6 ...
When reading posts at programming sites such as this one, I frequently encounter people saying things like: "There is no pass-by-reference in C, everything is passed by value." People claiming su...
I was fooling around with the following C code on my trusty old x86 PC: #include <stdint.h> #include <stdio.h> int main (void) { uint32_t u32 = 0xAABBCCDD; uint8_t* ptr = (u...
I have text (xml actually) files. Some files contain 'foo', some contain 'bar', some contain neither and some contain both. It's the both I'm interested in. How do I do an AND search on words in...
What does it mean that we can use memcmp(3) on invalid values? ISO C allows comparing an invalid value through memcmp(3), because it doesn't read the value, but rather its representation, and "rea...
When I want to print a number or a string, I can use f-strings (Python >= 3.6) or str.format, and I can use just the variable between braces, or use format specifiers. Ex: num, text = 10, 'abc' ...
Background Many Python programs now recommend installing with pipx, and there is a sense that you shouldn't install with pip anymore, you should use tools like pipx. Main Question However, what ...
This is a rather vague question, but I'm trying to solve a specific problem and I'm inexperienced in most of the potential solutions, so please forgive the inherent ambiguity. I have access to a d...
In git I branched feature-A from master. To reduce eventual merge conflicts later, I branched feature-B, which heavily overlaps and depends on A, from feature-A. A build of the feature-B branch s...
This is meant as a FAQ Q&A regarding variable-length arrays (VLA). The two bugs described below are surprisingly common. I'm trying to use the variable-length arrays feature of C99 (and newe...
I am working on a website which unfortunately uses a mix of linked and inline CSS and Javascript (and, even more unfortunately, I can't do a lot about the use of inline CSS and Javascript), and am ...
Functions in C have external linkage by default. In other words, the storage class specifier extern is applied to functions by default, with the effect that they are visible to all translation unit...
Note: I asked this question on TopAnswers a couple weeks ago, but didn't get any response, so I figured I'd ask it here. I am currently learning C++. I have a parent class (Vehicle) and two subc...
I manage a wsgi application that accepts JSON data via POST from potentially untrusted sources. Normally it is treated as a text blob and never parsed, but there is a value in the expected input th...
Is it valid to partly allocate an object, as long as you only use the allocated part of it? #include <stdio.h> #include <stdlib.h> struct s { int i[100]; }; int main(void) {...
For some reason, I just wanted to undo a commit on my git repository, which I've done with the following command: git reset --soft HEAD~1 So far, so good. However, by mistake I issued the comma...
How do I delete contents of a specific field, if it matches a pattern, and there is nothing else in the field? I have a several GB tsv file, and I am interested in a specific field (72). If it cont...
It would seem that the C standard library is a collection of diverse functions that pretty much just ended up in the standard by tradition or "accident", rather than through some careful plan or ra...
As a relative newcomer to Rust, I'm trying to understand the behaviour of lifetimes, but I am confused by the following code: let s: &str = "first"; let mut r: &str = s; println!("First ...
