On Saturday, April 30, 2016 01:32:54 AM Hans wrote: > On 30/04/16 00:28, Michael Mol wrote: > > On Friday, April 29, 2016 10:56:28 PM Hans wrote: > >> On 28/04/16 22:22, Hans wrote: > >> Kernel 4.4.6 as a bug. x11-drivers/xf86-video-virtualbox does not > >> compile. > >> Reason: > >> /usr/src/linux-4.4.6-gentoo/include/linux/string.h > >> 'char *strreplace(char *s, char old, char new);' causes compile failure. > >> "new" is a C++ keyword. > >> Changing tp 'char *strreplace(char *s, char oldstr, char newstr);' fixes > >> the problem. > > > > That's not a bug in the kernel per se, that's a bug in using that kernel > > header (written in C) in a compiler expecting C++ code. Which would make > > it a bug in xf86-video-virtualbox for not linking against a C-compiled > > object file. > > > > Granted, it'd be a heck of a lot more convenient if the kernel header > > files > > didn't use C++ keywords...but it *is* fundamentally a problem with > > compiling a source file using the wrong language. Like trying to read > > something in Portugese, except it was written in Spanish. It might work > > some of the time, but it'll catch you out eventually. > > The Virtualbox internal runtime compiler, assembler and gcc compiler to > build executables such as app-emulation/virtualbox-guest-additions, etc. > use some of the kernel sources and headers.
Assuming those components are using this string.h header file, that just means that those components are correctly treating treating these header files as C header files, and not C++ header files. > > Kernel 4.1.12 string.h and earlier did not have this silly problem. That just means that Kernel 4.1.12 string.h and earlier weren't exposing a bug in xf86-video-virtualbox. The Linux kernel is written in C with a smattering of platform-specific assembler, and some other used languages at build time. The header files for Linux are written in C. It's built with a C compiler. It's expected to be consumed by things expecting to be consuming C. xf86-video-virtualbox is trying to build C code in a C++ environment, and that's not guaranteed to work. In fact, it's semantically broken, as C isn't simply a subset of C++, nor is C++ simply a superset of C. They're two distinct languages that can be made to work reliably together if you pay attention, and the VirtualBox developers...didn't. Linux promises a stable ABI for existing API calls, but the symbol name for an *argument* of an API call isn't part of the ABI; functions' arguments' names aren't preserved at compile time. Similarly, adding new API calls doesn't disrupt existing API calls or the ABI, so adding a new API call with an argument named 'new' doesn't violate that ABI promise. Now, an argument can be made that the kernel developers working in C shouldn't use C++ keywords, but that's a dangerous slippery slope; there are a *lot* of languages out there that are superficially syntactically (and even semantically) similar to C, but *aren't*. What makes C++ special enough that the kernel should respect it, but not every other language? No...userland is built around the kernel, not the other way around--that's what makes it the kernel. The kernel has a fairly well-defined set of rules in that it's written in a supremely common standardized language, and there exist good practices for interfacing code written in that language with code written in other languages. I get that it's frustrating. Just trying to help you understand what's going on a a lower level, and why. -- :wq
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