portability – Tarik Billa

What’s the best C++ way to multiply unsigned integers modularly safely?

January 9, 2024 by Tarik

Some template metaprogramming with SFINAE, perhaps. #include <type_traits> template <typename T, typename std::enable_if<std::is_unsigned<T>::value && (sizeof(T) <= sizeof(unsigned int)) , int>::type = 0> T safe_multiply(T a, T b) { return (unsigned int)a * (unsigned int)b; } template <typename T, typename std::enable_if<std::is_unsigned<T>::value && (sizeof(T) > sizeof(unsigned int)) , int>::type = 0> T safe_multiply(T a, T b) { … Read more

Portable Compare And Swap (atomic operations) C/C++ library?

December 30, 2023 by Tarik

OPA (Open Portable Atomics) could be a good fit for your needs. https://trac.mcs.anl.gov/projects/openpa/ It provides a consistent C API to common atomic operations across multiple platforms under an MIT-style license. The library is small and certainly meets your size requirements. The current platform list is: GCC inline assembly for x86, x86_64, ia64, PPC 440, and … Read more

Final output on slave pty is lost if it was not closed in parent. Why?

December 29, 2023 by Tarik

I think there is unique separate behaviour for the Pty. The system terminates if the last data is written The system terminates if the child exits (broken pipe?) The code relies on the pipe existing long enough to send the data through, but the child exiting may cause the virtual channel to be deleted before … Read more

How portable is mktemp(1)?

December 26, 2023 by Tarik

POSIX does not seem to specify mktemp(1). It looks like most modern systems have it, but the available functionality and the semantics of the options vary between implementations (so particular invocations may not be portable): mktemp(1) from OpenBSD — mktemp(1) originated in OpenBSD 2.1 mktemp(1) from FreeBSD mktemp(1) from Mac OS X — almost always … Read more

How to write portable code in c++?

December 22, 2023 by Tarik

learn to use the standard library read books (eg. this one) when you’re experienced, learn to use boost

What is portability? How is java more portable than other languages? [closed]

December 19, 2023 by Tarik

Portability isn’t a black and white, yes or no kind of thing. Portability is how easily one can I take a program and run it on all of the platforms one cares about. There are a few things that affect this. One is the language itself. The Java language spec generally leaves much less up … Read more

Preventing MSYS ‘bash’ from killing processes that trap ^C

December 17, 2023 by Tarik

I had the exact same problem – I had written a program with a SIGINT/SIGTERM handler. That handler did clean-up work which sometimes took awhile. When I ran the program from within msys bash, ctrl-c would cause my SIGINT handler to fire, but it would not finish – the program was terminated (“from the outside”, … Read more

How should I handle “cast from ‘void*’ to ‘int’ loses precision” when compiling 32-bit code on 64-bit machine?

September 24, 2023 by Tarik

The issue is that, in 32bits, an int (which is a 32bit integer) will hold a pointer value. When you move to 64bit, you can no longer store a pointer in an int – it isn’t large enough to hold a 64bit pointer. The intptr_t type is designed for this.

c++ Initializing a struct with an array as a member

September 22, 2023 by Tarik

c++ doesn’t have the same flexible array member as last element as c99. You should use a std::vector if you don’t know how many elements or you should specify how many if you do. EDIT: You have said in your edit that the array is a runtime constant, so specify the size and it should … Read more

Correct, portable way to interpret buffer as a struct

September 4, 2023 by Tarik

I guess this is what I’ve been trying to avoid, but I finally went and took a look at the C99 standard myself. Here’s what I’ve found (emphasis added): §6.3.2.2 void 1 The (nonexistent) value of a void expression (an expression that has type void) shall not be used in any way, and implicit or … Read more