Messages in this thread | | | Date | Tue, 24 Jun 2014 00:50:07 +0100 (BST) | From | "Maciej W. Rozycki" <> | Subject | GCC version requirement (was: Re: mips: math-emu: Fix compilation error ieee754.c) |
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On Wed, 11 Jun 2014, David Rientjes wrote:
> > > ieee754dp has bitfield member in struct without name. And this > > > cause compilation error. This patch removes struct in ieee754dp > > > declaration. So compilation error is fixed. > > > Signed-off-by: Eunbong Song <eunb.song@samsung.com> > > > > What gcc version are you using? > > > > make arch/mips/math-emu/ieee754.o for mips defconfig triggers the > following on linux-next 30 times: > > arch/mips/math-emu/ieee754.c:45:2: error: unknown field 'sign' specified in initializer > arch/mips/math-emu/ieee754.c:45:2: warning: missing braces around initializer > arch/mips/math-emu/ieee754.c:45:2: warning: (near initialization for '__ieee754dp_spcvals[0].<anonymous>') > arch/mips/math-emu/ieee754.c:45:2: error: unknown field 'bexp' specified in initializer > arch/mips/math-emu/ieee754.c:45:2: warning: excess elements in union initializer > arch/mips/math-emu/ieee754.c:45:2: warning: (near initialization for '__ieee754dp_spcvals[0]') > arch/mips/math-emu/ieee754.c:45:2: error: unknown field 'mant' specified in initializer > arch/mips/math-emu/ieee754.c:45:2: warning: excess elements in union initializer > arch/mips/math-emu/ieee754.c:45:2: warning: (near initialization for '__ieee754dp_spcvals[0]') > > I'm using gcc 4.5.1 for mips. The patch makes all members part of the > union so it's probably not what you want to fix it, though.
There's more recent breakage like this, e.g.:
mm/page_io.c: In function '__swap_writepage': mm/page_io.c:277: error: unknown field 'bvec' specified in initializer mm/page_io.c:278: warning: excess elements in struct initializer mm/page_io.c:278: warning: (near initialization for 'from')
introduced with "bio_vec-backed iov_iter" (GCC 4.1.2 here). We still in principle support GCC versions back to 3.2:
$ grep 'Gnu C' Documentation/Changes o Gnu C 3.2 # gcc --version $
so either this breakage has to be cleaned up or the requirement for the minimum GCC version revisited.
This is a semi-standard language extension BTW, citing from the GCC manual:
-------------------------------------------------------------------------- 6 Extensions to the C Language Family *************************************
GNU C provides several language features not found in ISO standard C. (The `-pedantic' option directs GCC to print a warning message if any of these features is used.) To test for the availability of these features in conditional compilation, check for a predefined macro `__GNUC__', which is always defined under GCC.
6.59 Unnamed struct/union fields within structs/unions ======================================================
As permitted by ISO C11 and for compatibility with other compilers, GCC allows you to define a structure or union that contains, as fields, structures and unions without names. --------------------------------------------------------------------------
-- note the term "permitted" rather than "required".
We do make use of a few GCC language extensions, most notably inline assembly, however in this case we merely save a couple of characters here and there and this is IMO not worth breaking people's development environments.
Maciej
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