Re: Building gcc6.3.0 on Ubuntu-20.04

[Mohana <s18002@students.iitmandi.ac.in>]

MATLAB can only work with GCC6.3.0 (
https://in.mathworks.com/matlabcentral/answers/407502-incompatible-gcc-version-with-mex),
so I hope to get this working, if possible. I applied the changes to file
sanitizer_platform_limits_posix.cc as per the patch, and now the error is:

In file included from
/home/mohana/gccbuild/../gcc-6.3.0/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc:192:0:
/home/mohana/gccbuild/../gcc-6.3.0/libsanitizer/sanitizer_common/sanitizer_internal_defs.h:254:72:
error: size of array ‘assertion_failed__1142’ is negative
     typedef char IMPL_PASTE(assertion_failed_##_, line)[2*(int)(pred)-1]
                                                                        ^
/home/mohana/gccbuild/../gcc-6.3.0/libsanitizer/sanitizer_common/sanitizer_internal_defs.h:248:30:
note: in expansion of macro ‘IMPL_COMPILER_ASSERT’
 #define COMPILER_CHECK(pred) IMPL_COMPILER_ASSERT(pred, __LINE__)
                              ^~~~~~~~~~~~~~~~~~~~
/home/mohana/gccbuild/../gcc-6.3.0/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h:1410:3:
note: in expansion of macro ‘COMPILER_CHECK’
   COMPILER_CHECK(sizeof(((__sanitizer_##CLASS *) NULL)->MEMBER) == \
   ^~~~~~~~~~~~~~
/home/mohana/gccbuild/../gcc-6.3.0/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc:1142:1:
note: in expansion of macro ‘CHECK_SIZE_AND_OFFSET’
 CHECK_SIZE_AND_OFFSET(ipc_perm, mode);
 ^~~~~~~~~~~~~~~~~~~~~
make[4]: *** [Makefile:477: sanitizer_platform_limits_posix.lo] Error 1
make[4]: Leaving directory
'/home/mohana/gccbuild/x86_64-pc-linux-gnu/libsanitizer/sanitizer_common'
libtool: link: (cd ".libs" && rm -f "libatomic.so" && ln -s
"libatomic.so.1.2.0" "libatomic.so")
make[3]: *** [Makefile:466: all-recursive] Error 1

I hope I applied the patch correctly, just removed the lines with (-) and
added ones with (+).

On Tue, Aug 18, 2020 at 6:45 PM Jonathan Wakely <jwakely.gcc@gmail.com>
wrote:

> On Tue, 18 Aug 2020 at 12:07, Mohana <s18002@students.iitmandi.ac.in>
> wrote:
> >
> > I made the changes and this error doesn't occur anymore, but the
> following happens now:
> >
> >
> /home/mohana/gccbuild/../gcc-6.3.0/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc:158:23:
> fatal error: sys/ustat.h: No such file or directory
> >  #include <sys/ustat.h>
> >                        ^
> > compilation terminated.
> > make[4]: *** [Makefile:477: sanitizer_platform_limits_posix.lo] Error 1
> > make[4]: *** Waiting for unfinished jobs....
> >
> > It seems ustat is deprecated. How can this be fixed?
>
> Why are you building gcc 6.3.0 and not 6.5.0, which already has the
> fix for both these problems?
>
> The patch for this error was
> https://gcc.gnu.org/g:2cd244789bc75ecdf65824f831986969049a1647
> specifically
> https://gcc.gnu.org/git/?p=gcc.git;a=blobdiff;f=libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc;h=98825b584d24912df76f9982c2319419c7815bf8;hp=6992f2cd8ac56bcd5102f7440d71137b4458871d;hb=2cd244789bc75ecdf65824f831986969049a1647;hpb=6376168efb4c45d621fbec6472f8c9e84a24e940
>
> But you should just use gcc-6.5.0 instead.
>