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From: "alipasha.celeris at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/52921] New: Memory errors when compiled with -fstrict-overflow flag
Date: Tue, 10 Apr 2012 02:13:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52921

             Bug #: 52921
           Summary: Memory errors when compiled with -fstrict-overflow
                    flag
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: alipasha.celeris@gmail.com


The following test code generates memory errors (valgrind : "Conditional jump
or move depends on uninitialised value(s)") when assigning the values to %CMP
components without allocating it first, if it is compiled with flag
-fstrict-overflow.

      PROGRAM QUICK_TEST

      TYPE COMP
        INTEGER, ALLOCATABLE :: CMP(:)
      END TYPE COMP
      TYPE COMP_ARRAY
        TYPE (COMP), ALLOCATABLE :: ARR(:)
      END TYPE COMP_ARRAY

      INTEGER :: I
      TYPE (COMP_ARRAY), TARGET :: MY_ARR

      READ *, I
      ALLOCATE (MY_ARR%ARR(I))
      MY_ARR%ARR(I)%CMP = [1, 2]

      END PROGRAM QUICK_TEST

However, if "READ *, I" is replaced with "I = 10", i.e. allocation size and the
array index are known at compile time, then no memory errors are generated.

Furthermore, this flag is included in -O3 optimization flag, but it is not
shown when compiling with -Q --help=optimizers .