When a process receives a signal from kill or pkill, it needs a signal handler to intercept and respond to it. Without one, most signals terminate the process immediately. This guide covers setting up robust signal handlers for production daemons. Understanding Signals The kill command sends signals to processes. By default, it sends SIGTERM (signal…
Memory leak detection is critical for C program reliability. Several tools work at different stages of development—compile time, runtime, and production scenarios. Your choice depends on performance tolerance, integration needs, and how much detail you require. AddressSanitizer (ASan) AddressSanitizer is the first tool to reach for in 2026. It’s compiler-integrated, fast, and catches a broader…
The @ symbol in Makefiles suppresses the echo of the command itself before execution. When you run a target, make normally prints each command to stdout before running it. Adding @ before a command hides that echo, showing only the command’s output. Basic example Without @: all: echo “For correctness test of basic get and…
Parsing directory and filename components from an absolute path is a common task in systems programming. Linux provides dirname() and basename() functions for this purpose, but they have implementation-specific behaviors that can cause bugs if you’re not careful. Using dirname() and basename() The POSIX standard defines both functions, though the implementations vary. Here’s the safest…
When you have shared Makefiles included across multiple projects in different directory structures, relative includes break. If common.mk tries to include release.mk and both files are in a subdirectory like external/, the include fails because Make uses the current working directory, not the location of the including file. For example, this structure works fine: Makefile…
Start by compiling your C source files into object files: gcc -c lib1.c lib2.c This produces lib1.o and lib2.o. You can use any compiler flags here—-Wall, -O2, -fPIC, etc.—that match your build requirements. Position-independent code (-fPIC) isn’t strictly required for static libraries but is good practice if you anticipate reusing these objects elsewhere. Creating the…
When you need to page through error output from a command, you’ll run into the issue that less only receives stdout by default. Error messages go to stderr (file descriptor 2), so they’ll still scroll past on your terminal while stdout gets paged. Basic approach: combine stderr with stdout make 2>&1 | less The 2>&1…
Designated initializers for aggregate types with non-trivial members (like std::vector) have inconsistent support across GCC versions. This error typically appears when you try to initialize a struct containing standard library containers using designated initializer syntax in the wrong order. The Problem When you compile this code with older GCC versions: struct Stat { vector<int> vec;…
The common claim that cin is significantly slower than scanf in C++ is partially true, but only when comparing default configurations. The reality is more nuanced. Why cin Can Be Slower by Default By default, C++ streams maintain synchronization with C stdio streams (stdin, stdout, stderr). This synchronization requires additional overhead because the library must…
Transactional memory (TM) is a synchronization mechanism that simplifies concurrent programming by allowing multiple threads to execute code atomically without explicit lock management. If you’re getting into this area, here are the best resources and practical approaches to build solid understanding. Foundational Reading The classic reference is still Transactional Memory by James R. Larus and…
Static linking embeds all library code directly into your executable, eliminating runtime dependencies on shared libraries. This approach trades disk space for portability and eliminates “library not found” errors at runtime. Basic Static Compilation To statically link a simple C program, use the -static flag: gcc -static -o myprogram myprogram.c For C++: g++ -static -o…
MySQL Cluster uses NDB (Network Database) storage engine to provide high availability and data redundancy across multiple nodes. This guide covers installation and configuration on modern RHEL-compatible systems. Prerequisites Three or more servers (minimum: one management node, two data nodes, one SQL node) Rocky Linux 9 or AlmaLinux 9 Root or sudo access Static IP…
The x86-64 architecture on Linux follows the System V AMD64 ABI calling convention. Understanding this is essential when writing assembly, optimizing code, debugging, or interfacing with C libraries. Register usage for arguments Integer and pointer arguments use these registers in order: RDI — first argument RSI — second argument RDX — third argument RCX —…
To enable debugging, configure your CMake build with CMAKE_BUILD_TYPE set to Debug. This tells CMake to invoke the compiler with the -g flag, generating debug symbols that tools like gdb and lldb need. From your project’s root directory: cmake -DCMAKE_BUILD_TYPE=Debug -B build cd build make The -B build flag creates a separate build directory, which…
ANSI C is the standardized version of C defined in 1989, specifying the language’s syntax and semantics formally through a grammar. Understanding this grammar is essential for building tools that parse, analyze, or transform C code. Grammar Basics The ANSI C grammar is defined using Backus-Naur Form (BNF), a notation for specifying formal grammars. The…
The conventional wisdom that smaller code is always better has been thoroughly invalidated on modern processors. A statement from kernel development circles captured this well: for performance-critical paths like interrupt handlers, large-but-correctly-aligned-and-optimized code consistently outperforms byte-packed alternatives. Consider this comparison: mov eax, [foo] add eax, 1 mov [foo], eax versus: inc [foo] The three-instruction sequence…
When you mmap() a range larger than your system’s total physical memory plus swap, the kernel normally reserves swap space to back the mapping. If that reservation would exceed available swap, mmap() fails with ENOMEM. The MAP_NORESERVE flag lets you bypass this reservation requirement. Understanding the Default Behavior By default, when you call mmap() with…
Before encoding instructions, you need to understand the two assembly syntaxes you’ll encounter—they differ fundamentally in operand order and addressing format. Intel syntax (Intel/AMD manuals): Operand order: destination, source Memory addressing: [base+offset] Example: add r8, [rdi+0xa] AT&T syntax (GNU toolchains on Linux): Operand order: source, destination Memory addressing: offset(%base) Example: addq 0xa(%rdi), %r8 For most…
Grab a release from kernel.org. Recent stable versions (6.x and later) are recommended for production systems: wget https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz tar xf linux-6.12.tar.gz cd linux-6.12/ If wget isn’t available, use curl: curl -O https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz Verify the tarball Always verify the kernel’s integrity using checksums and signatures published on kernel.org. This is essential for production systems: wget https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz.asc…
Picking your first programming language matters, but it’s not the career-defining decision some make it out to be. What matters more is that you pick something reasonable and start building. That said, some choices will save you months of frustration. Know What You’re Optimizing For Before evaluating languages, answer these questions honestly: What do you…