_GNU_SOURCE is the only one you should ever define yourself. __USE_GNU is defined internally through a mechanism in features.h (which is included by all other glibc headers) when _GNU_SOURCE is defined, and possibly under other conditions. Defining or undefining __USE_GNU yourself will badly break the glibc headers.
Starting with C++17 std::string_view is available. It supports constexpr comparisson: #include <string_view> constexpr bool strings_equal(char const * a, char const * b) { return std::string_view(a)==b; } int main() { static_assert(strings_equal(“abc”, “abc” ), “strings are equal”); static_assert(!strings_equal(“abc”, “abcd”), “strings are not equal”); return 0; } Demo
The technical term for ‘multiple files’ would be translation units: g++ file1.cpp file2.cpp -o program Or you separate compilation and linking g++ -c file1.cpp -o file1.o g++ -c file2.cpp -o file2.o # linking g++ file1.o file2.o -o program But that usually doesn’t make sense unless you have a larger project (e.g. with make) and want … Read more
No, fgets is not actually deprecated in C99 or the current standard, C11. But the author of that tutorial is right that fgets will not stop when it encounters a NUL, and has no mechanism for reporting its reading of such a character. The fgets function reads at most one less than the number of … Read more
You could try using objcopy to convert it to a normal object you can link in, and then reference its symbols in the linker script like you would do to a normal object. From the objcopy manual page: -B bfdarch –binary-architecture=bfdarch Useful when transforming a raw binary input file into an object file. In this … Read more
bash -n scriptname Perhaps an obvious caveat: this validates syntax but won’t check if your bash script tries to execute a command that isn’t in your path, like ech hello instead of echo hello.
Excerpt from info as (GNU Binutils 2.21.90), or online in the GAS manual: https://sourceware.org/binutils/docs/as/Dot.html 5.4 The Special Dot Symbol The special symbol . refers to the current address that as is assembling into. Thus, the expression melvin: .long . defines melvin to contain its own address. Assigning a value to . is treated the same … Read more
From the documentation for the ARM compiler (which is based on gcc): __attribute__((pure)) function attribute Many functions have no effects except to return a value, and their return value depends only on the parameters and global variables. Functions of this kind can be subject to data flow analysis and might be eliminated. __attribute__((const)) function attribute … Read more
As I was about to complete writing this question, I ran parallel –version to report the version, only to find: WARNING: YOU ARE USING –tollef. IF THINGS ARE ACTING WEIRD USE –gnu. It is not clear to me why that flag is set by default. Needless to say, using –gnu worked! Thought I would post … Read more
fseek64 is a C function. To make it available you’ll have to define _FILE_OFFSET_BITS=64 before including the system headers That will more or less define fseek to be actually fseek64. Or do it in the compiler arguments e.g. gcc -D_FILE_OFFSET_BITS=64 …. http://www.suse.de/~aj/linux_lfs.html has a great overviw of large file support on linux: Compile your programs … Read more