Date: Thu, 23 Dec 2021 11:13:01 -0800 From: Colin Cross <ccross@...gle.com> To: musl@...ts.openwall.com Cc: Ismael Luceno <ismael@...ev.co.uk> Subject: Re: [PATCH] Define NULL as nullptr when used in C++ On Sun, Aug 15, 2021 at 05:51:57PM +0200, Ismael Luceno wrote: > This should be safer for casting and more compatible with existing code > bases that wrongly assume it must be defined as a pointer. This seems to meet the C++ spec for NULL , but I noticed some compatibility issues with code that was previously compiling with glibc. I've found multiple places that used reinterpret_cast<int*>(NULL), which now fail with: error: reinterpret_cast from 'nullptr_t' to 'int *' is not allowed According to  those should technically be static_cast and not reinterpret_cast. I've also seen failures with returning NULL from a function with a jlong return type: error: cannot initialize return object of type 'jlong' (aka 'long') with an rvalue of type 'nullptr_t' glibc uses __null if __GNUG__ is set, ((void*)0) for __cplusplus, or 0 for C. This also meets the C++ spec for NULL , but is an improvement over the previous 0L because it can be correctly interpreted as a NULL sentinel value by Clang's -Wsentinel warning. Ismael, can you give an example of the code that assumes NULL is a pointer? Does it work with __null (assuming you're using a compiler that has GNU extensions like __null)? In any case, I'll fix the technically incorrect code I have access to so that it works with nullptr.  https://en.cppreference.com/w/cpp/types/NULL  https://en.cppreference.com/w/cpp/language/reinterpret_cast
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