Martin Sebor <msebor@xxxxxxxxx> writes: > On 11/09/2015 12:38 PM, Sergey Organov wrote: >> Martin Sebor <msebor@xxxxxxxxx> writes: >> >>> On 11/09/2015 05:57 AM, Sergey Organov wrote: >>>> Hello, >>>> >>>> GCC, when compiling C code, seems to always generate out-of-line copy of >>>> any [C99] inline function that also happens to be a GCC builtin, >>>> resulting in link errors (see a test-case below). According to C99 >>>> standard, an out-of-line copy of a function should only be instantiated >>>> in those compilation unit(s) where the function is also declared >>>> 'extern'. >>>> >>>> Apparently, all builtin functions implicitly get 'extern' declaration that >>>> forces out-of-line copy of inline function in every compilation unit. >>>> >>>> Is it a bug of feature? If the latter, what is the way for a library to >>>> provide generic inline functions that might happen to be GCC builtins? >>> >>> Depending on the -std= option, GCC can generate a copy of an inline >>> function (regardless of whether or not the function also has a builtin >>> form) in each translation unit that defines it. To avoid multiple >>> definition errors, define inline functions in C headers as static. >>> >>> The following page explains how GCC treats the inline specifier >>> in each of the standard mode: >>> >>> https://gcc.gnu.org/onlinedocs/gcc/Inline.html >> >> The point is that for builtin functions it apparently does it wrong. > > I see. Yes, that does look like a bug. symtab_node::needed_p() > returns false for an ordinary inline function but true for one > that has a builtin. I didn't spend enough time debugging this > to see what sets it and why, and I couldn't find any tests for > this to confirm that it's deliberate. > > On the other hand, speaking in the strict C sense, abs and most > (all?) such symbols that have corresponding builtins are reserved > in a hosted implementation so defining them is undefined. They are > only allowed to be defined in a freestanding environment. Yeah, freestanding environment is what I care about. > In any event, you should probably open a bug so that someone who > knows more about the implementation than I do can say for sure. OK, thanks, will do. -- Sergey.
