> > > > Date: Tue, 21 Jan 2020 11:05:37 -0500 > From: Steve Grubb <sgrubb@xxxxxxxxxx> > Subject: Re: gcc 10: Default to -fno-common, multiple definitions of > ... > To: devel@xxxxxxxxxxxxxxxxxxxxxxx > Cc: Jakub Jelinek <jakub@xxxxxxxxxx> > Message-ID: <4127758.jL2Gs7s9Fr@x2> > Content-Type: text/plain; charset="UTF-8" > > On Tuesday, January 21, 2020 7:35:03 AM EST Miro Hrončok wrote: > > This is a known thing in gcc 10: > > > > https://gcc.gnu.org/gcc-10/porting_to.html#common > > > > "Default to -fno-common > > > > A common mistake in C is omitting extern when declaring a global variable > > in a header file. If the header is included by several files it results in > > multiple definitions of the same variable. In previous GCC versions this > > error is ignored. GCC 10 defaults to -fno-common, which means a linker > > error will now be reported. To fix this, use extern in header files when > > declaring global variables, and ensure each global is defined in exactly > > one C file. As a workaround, legacy C code can be compiled with -fcommon. > > > > > > int x; // tentative definition - avoid in header files > > > > extern int y; // correct declaration in a header file" > > So, for those of us using F31 as the development / test environment, is there > a macro that we can add -fno-common to in ~/.rpmmacros without placing it in > the %__global_compiler_flags in /usr/lib/rpm/redhat/macros ? > > Looking for an easy way to reproduce this without modifying root owned files. > > -Steve > > > ------------------------------ > > Date: Tue, 21 Jan 2020 17:27:20 +0100 > From: Miro Hrončok <mhroncok@xxxxxxxxxx> > Subject: Re: gcc 10: Default to -fno-common, multiple definitions of > ... > To: Steve Grubb <sgrubb@xxxxxxxxxx>, devel@xxxxxxxxxxxxxxxxxxxxxxx > Message-ID: <0f655139-44f5-a0c5-b600-66614c8bd6d6@xxxxxxxxxx> > Content-Type: text/plain; charset=utf-8; format=flowed > > On 21. 01. 20 17:05, Steve Grubb wrote: > > On Tuesday, January 21, 2020 7:35:03 AM EST Miro Hrončok wrote: > > > This is a known thing in gcc 10: > > > > > > https://gcc.gnu.org/gcc-10/porting_to.html#common > > > > > > "Default to -fno-common > > > > > > A common mistake in C is omitting extern when declaring a global variable > > > in a header file. If the header is included by several files it results in > > > multiple definitions of the same variable. In previous GCC versions this > > > error is ignored. GCC 10 defaults to -fno-common, which means a linker > > > error will now be reported. To fix this, use extern in header files when > > > declaring global variables, and ensure each global is defined in exactly > > > one C file. As a workaround, legacy C code can be compiled with -fcommon. > > > > > > > > > int x; // tentative definition - avoid in header files > > > > > > extern int y; // correct declaration in a header file" > > > > So, for those of us using F31 as the development / test environment, is there > > a macro that we can add -fno-common to in ~/.rpmmacros without placing it in > > the %__global_compiler_flags in /usr/lib/rpm/redhat/macros ? > > > > Looking for an easy way to reproduce this without modifying root owned files. > > You should be able to redefine %__global_compiler_flags in ~/.rpmmacros. > It still means you need to copy paste the current flags, but you won't need to > touch root owned files. I proposed a change to redhat-rpm-config to handle this case by allowing package to add a single line to their .spec file to turn off the new common symbol handling. Igor rejected that change arguing that the packages themselves should be fixed. Jeff _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
