https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83705
Bug ID: 83705
Summary: [8 Regression] ICE with large values of REPEAT after
revision r256284
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: dominiq at lps dot ens.fr
CC: jb at gcc dot gnu.org
Target Milestone: ---
The following variant of the second test at
https://gcc.gnu.org/ml/fortran/2017-12/msg00132.html
program main
integer(8), parameter :: n=2_8**28 - 1_8
character(len=*), parameter :: a1 = repeat('x',n)
end program main
compiles with gfortran 7.2.0 and trunk before r256284.
If I replace 2_8**28 - 1_8 with 2_8**28, I get the following ICE
f951(30823,0x7fff9211a340) malloc: *** mach_vm_map(size=18446744073441116160)
failed (error code=3)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
f951: out of memory allocating 18446744073441116160 bytes after a total of 0
bytes
If I compile the test with an instrumented compiler (r256049), I get
../../p_work/gcc/fortran/trans-const.c:100:17: runtime error: signed integer
overflow: 8 * 268435456 cannot be represented in type 'int'
(with an earlier revision I also got
../../p_work/gcc/fortran/target-memory.c:71:17: runtime error: signed integer
overflow: 1073741824 * 8 cannot be represented in type ‘int’
)
With an instrumented version of r256284 I got
../../work/gcc/fortran/decl.c:1748:37: runtime error: member access within null
pointer of type 'struct gfc_expr'
for 'n' as small as 2_8**23 + 1_8. I think it is due to the patch
- nlen = ncop * len;
+ gfc_charlen_t nlen = ncop * len;
+
+ /* Here's a semi-arbitrary limit. If the string is longer than 32 MB
+ (8 * 2**20 elements * 4 bytes (wide chars) per element) defer to
+ runtime instead of consuming (unbounded) memory and CPU at
+ compile time. */
+ if (nlen > 8388608)
+ return NULL;
which makes sense for variables, but IMO not for parameters.
If I revert this patch, the following test
program main
integer(8), parameter :: n=2_8**32
character(len=n) :: a1 = repeat('x',n)
character(len=3) :: a2, a3
print *, len(a1, kind=8)
a2 = a1(1:3)
a3 = a1(n-2:n)
print *, "'", a2, "', '", a3, "'"
end program main
! https://gcc.gnu.org/ml/fortran/2017-12/msg00132.html
compiles and gives at run time
4294967296
'', ''
Note the empty strings a2 and a3.
With the patch reverted the test gfortran.dg/repeat_7.f90 gives
f951: out of memory allocating 18446744073709551615 bytes after a total of 0
bytes
as well as the first test in this comment with n=2_8**28 (while it compiles
with n=2_8**32).
For n=2_8**28, my instrumented compiler reports
../../work/gcc/fortran/trans-const.c:100:17: runtime error: signed integer
overflow: 8 * 268435456 cannot be represented in type 'int'
