Bug#888422: libmpfr6 should add Breaks: libmpfr4

[Julien Cristau <jcristau@debian.org>]

Control: severity -1 normal
Control: tag -1 moreinfo

On Thu, Jan 25, 2018 at 14:11:49 +0200, Adrian Bunk wrote:

> Package: libmpfr6
> Version: 4.0.0-5
> Severity: serious
> 
> Mixing libmpfr4 and libmpfr6 doesn't work well:
> 
> flint-arb FTBFS with:
> /usr/bin/ld: warning: libmpfr.so.4, needed by /usr/lib/libflint.so, may conflict with libmpfr.so.6
> /usr/bin/ld: mpfr_free_func: TLS definition in //usr/lib/x86_64-linux-gnu/libmpfr.so.4 section .tbss mismatches non-TLS definition in /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libmpfr.so section .text
> //usr/lib/x86_64-linux-gnu/libmpfr.so.4: error adding symbols: Bad value
> collect2: error: ld returned 1 exit status
> 
> Some packages like fractalnow FTBFS when gcc and libmpc3 use
> different mpfr libraries, with a gcc ICE:
> ../../src/init2.c:52: MPFR assertion failed: p >= 2 && p <= ((mpfr_prec_t)((mpfr_uprec_t)(~(mpfr_uprec_t)0)>>1))
> src/fractal_compute_engine.c: In function 'FractalLoopMANDELBROTPINTAVERAGECOLORINGDISCRETECURVATURENONESINGLE':
> src/fractal_compute_engine.c:285:1: internal compiler error: Aborted
> 
> It is not even obvious in the latter case that this is always only an ICE,
> and not sometimes a miscompilation.
> 
> The libmpc3 issue is also expected to hit users who have older gcc versions
> still installed, e.g. gcc-6 still installed after stretch->buster upgrade.
> 
> When the dependencies are fulfilled users can expect to have working software,
> even a forced removal on stretch->buster upgrades is better than runtime problems.

Is this actually a problem between libmpfr4 and libmpfr6, or libmpfr4
and the new libmpfr-dev?  A Breaks relationship between libmpfr4 and
libmpfr6 would be very, very bad.

Cheers,
Julien