[Bug fortran/87352] New: Large stack usage with new gfortran

[jeremy at jeremysanders dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87352

            Bug ID: 87352
           Summary: Large stack usage with new gfortran
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jeremy at jeremysanders dot net
  Target Milestone: ---

Created attachment 44718
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44718&action=edit
Affected module and example main program

With gcc/gfortran 7.3 and 8.2, creation of a variable in the main program with
a particular type defined in a module (attached) leads to a segfault due to
very large stack usage. This worked on gcc 4.8.4 and earlier versions.

In addition compilation of the module creates an object file which is x10000
times larger than for earlier gcc versions (200MB vs 25KB). With optimization
(-O2), the compilation time is several minutes, rather than less than a second.

Instructions for compilation:

$ gfortran -ffixed-line-length-none -ffree-line-length-none -g -O2 -o testcomb
testcomb.f90 
testcomb.f90:1303:0:

 end module  testmodule

note: variable tracking size limit exceeded with -fvar-tracking-assignments,
retrying without
$ ./testcomb 
$ gdb ./testcomb 
GNU gdb (Ubuntu 8.1-0ubuntu3) 8.1.0.20180409-git
...
(gdb) run
Starting program: /home/jsanders/tmp/foo/testcomb 

Program received signal SIGSEGV, Segmentation fault.
testprog () at testcomb.f90:1309
1309      type(instlist_type),target    :: instlist

It works if the stack is increased to 819200.

This problem is seen using Ubuntu Bionic (18.04) on x86-64, using the built-in
gcc (7.3.0), or a self-compiled version (8.2.0) with no special build options.