MacPorts gcc 9.3.0 internal compiler error: Segmentation fault: 11 - not seen with Homebrew gcc 9.3.0

[attiliodefalco]

The following code fails to compile with MacPorts gcc 9.3.0 but not Homebrew gcc 9.3.0

#include <math.h>
 double vec_dist ()
 {double r=0;
 return sqrt(r);
 }

And compile with:

gcc -O2 -ffast-math -c test.c

The output is:

test.c: In function 'vec_dist':
test.c:6:1: internal compiler error: Segmentation fault: 11
}
^
test.c:6:1: internal compiler error: Abort trap: 6
gcc: internal compiler error: Abort trap: 6 (program cc1)

This reproduces on my 4-year old laptop, but not my 5-year old mini. Both are currently running 10.15.4 (usually the mini runs betas) and have gcc 9.3.0 from MacPorts. On the laptop, this segfaults the compiler when compiled with '-O2 -ffastmath':

extern double sqrt(double); double mad_vec_dist () { double r=0; return sqrt(r); }

(note that I removed the include of math.h). Changing sqrt() to sin() also segfaults. However, this compiles fine:

extern double trqs(double); double vec_dist () { double r=0; return trqs(r); }

and the ones that segfault the compiler don't segfault if I add the '-fno-builtin' flag--so it's something about the optimization of the builtin math functions that are enabled by -ffastmath. This is likely actually a bug in the upstream gcc but I don't see the segfault with Homebrew gcc 9.3 (or even on CentOS 7 gcc 9.3).

Please let me know if I should notify GNU, as well.

Thanks!

Attilio