https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96018
Bug ID: 96018
Summary: Optimization issue with external HDF5 library
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: martin.schlipf at damnthespam dot com
Target Milestone: ---
Created attachment 48817
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48817&action=edit
Minimal example to demonstrate the issue.
On a clean Ubuntu 20.04 with the following setup
sudo apt-get update
sudo apt-get install gfortran-10
sudo apt-get install libhdf5-dev
the attached code produces an error when compiled with optimization
gfortran-10 -O2 hdf5_bug.f90 -I/usr/include/hdf5/serial/
-L/usr/lib/x86_64-linux-gnu/ -lhdf5_serial_fortran
As far as I can tell, the reason this appears is that the compiler fails to
recognize that the function call in line 98 has side effects and optimizes it
away. If you check the status of the error code, the issue disappears.
Strangely, the exact same sequence of calls with a 2d array instead of a 3d one
works fine.
