musl - musl - an implementation of the standard library for Linux-based systems

Age	Commit message (Collapse)	Author	Lines
2021-11-29	define NULL as nullptr when used in C++11 or later	Ismael Luceno	-1/+3
	This should be safer for casting and more compatible with existing code bases that wrongly assume it must be defined as a pointer.
2013-11-24	restore type of NULL to void * except when used in C++ programs	Rich Felker	-0/+4
	unfortunately this eliminates the ability of the compiler to diagnose some dangerous/incorrect usage, but POSIX requires (as an extension to the C language, i.e. CX shaded) that NULL have type void . plain C allows it to be defined as any null pointer constant. the definition 0L is preserved for C++ rather than reverting to plain 0 to avoid dangerous behavior in non-conforming programs which use NULL as a variadic sentinel. (it's impossible to use (void )0 for C++ since C++ lacks the proper implicit pointer conversions, and other popular alternatives like the GCC __null extension seem non-conforming to the standard's requirements.)
2013-08-02	fix feature test macro logic for _BSD_SOURCE	Rich Felker	-1/+1
	in several places, _BSD_SOURCE was not even implying POSIX, resulting in it being subtractive rather than additive (compared to the default features).
2013-01-18	use a common definition of NULL as 0L for C and C++	Rich Felker	-6/+1
	the historical mess of having different definitions for C and C++ comes from the historical C definition as (void )0 and the fact that (void )0 can't be used in C++ because it does not convert to other pointer types implicitly. however, using plain 0 in C++ exposed bugs in C++ programs that call variadic functions with NULL as an argument and (wrongly; this is UB) expect it to arrive as a null pointer. on 64-bit machines, the high bits end up containing junk. glibc dodges the issue by using a GCC extension __null to define NULL; this is observably non-conforming because a conforming application could observe the definition of NULL via stringizing and see that it is neither an integer constant expression with value zero nor such an expression cast to void. switching to 0L eliminates the issue and provides compatibility with broken applications, since on all musl targets, long and pointers have the same size, representation, and argument-passing convention. we could maintain separate C and C++ definitions of NULL (i.e. just use 0L on C++ and use (void )0 on C) but after careful analysis, it seems extremely difficult for a C program to even determine whether NULL has integer or pointer type, much less depend in subtle, unintentional ways, on whether it does. C89 seems to have no way to make the distinction. on C99, the fact that (int)(void )0 is not an integer constant expression, along with subtle VLA/sizeof semantics, can be used to make the distinction, but many compilers are non-conforming and give the wrong result to this test anyway. on C11, _Generic can trivially make the distinction, but it seems unlikely that code targetting C11 would be so backwards in caring which definition of NULL an implementation uses. as such, the simplest path of using the same definition for NULL in both C and C++ was chosen. the #undef directive was also removed so that the compiler can catch and give a warning or error on redefinition if buggy programs have defined their own versions of NULL prior to inclusion of standard headers.
2012-09-07	default features: make musl usable without feature test macros	Rich Felker	-0/+2
	the old behavior of exposing nothing except plain ISO C can be obtained by defining __STRICT_ANSI__ or using a compiler option (such as -std=c99) that predefines it. the new default featureset is POSIX with XSI plus _BSD_SOURCE. any explicit feature test macros will inhibit the default. installation docs have also been updated to reflect this change.
2011-02-14	more header cleanup and conformance fixes - locale.h, time.h	Rich Felker	-1/+2

2011-02-12	initial check-in, version 0.5.0v0.5.0	Rich Felker	-0/+84