Le 09/03/2020 à 14:46, Pierre Labastie via blfs-dev a écrit : > Le 09/03/2020 à 13:43, Bruce Dubbs via blfs-dev a écrit : >> On 3/8/20 10:49 PM, Xi Ruoyao via blfs-dev wrote: >>> GCC 10 will enable -fno-common by default. It would break some "legacy" >>> (actually buggy IMO) code. I found some cases in the book with GCC 9 and >>> -fno- >>> common explicitly enabled. >>> >>> Patches uploaded to >>> http://www.linuxfromscratch.org/~xry111/fno-common-patches/. >>> I hope the upstream can fix these cases before GCC 10 (for SDL2, xorg-server >>> and >>> pipewire the fix is already commited). But if they don't we can grab these >>> patches as needed. >> >> Thanks for that. One question though. When I go to >> https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html is says >> >> "The default is -fno-common, which specifies that the compiler places >> uninitialized global variables in the BSS section of the object file. This >> inhibits the merging of tentative definitions by the linker so you get a >> multiple-definition error if the same variable is accidentally defined in >> more >> than one compilation unit." >> >> I would read the above to indicate that -fno-common is default for gcc9 also. >> >> Comments? >> > > In the info file for gcc-9.2.0: > > Unix C compilers have traditionally allocated storage for > uninitialized global variables in a common block. This allows the > linker to resolve all tentative definitions of the same variable in > different compilation units to the same object, or to a > non-tentative definition. This is the behavior specified by > '-fcommon', and is the default for GCC on most targets. On the > other hand, this behavior is not required by ISO C, and on some > targets may carry a speed or code size penalty on variable > references. > > So I think the internet version is for GCC 10.
The right address for internet doc for 9.2.0 is https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/ Pierre -- http://lists.linuxfromscratch.org/listinfo/blfs-dev FAQ: http://www.linuxfromscratch.org/blfs/faq.html Unsubscribe: See the above information page
