# Building MPICH as an external project results in an odd fortran error - FCMODOUTFLAG not detected.

**URL:** https://discourse.cmake.org/t/building-mpich-as-an-external-project-results-in-an-odd-fortran-error-fcmodoutflag-not-detected/927
**Category:** Code
**Tags:** os:linux, comp:gcc, gen:makefiles, lang:fortran
**Created:** [April 2, 2020, 2:58pm UTC](https://discourse.cmake.org/t/building-mpich-as-an-external-project-results-in-an-odd-fortran-error-fcmodoutflag-not-detected/927 "2020-04-02T14:58:58Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![KBentley57](https://discourse.cmake.org/user_avatar/discourse.cmake.org/kbentley57/32/474_2.png) [@KBentley57](https://discourse.cmake.org/u/KBentley57)
#### Post date: [April 2, 2020, 2:58pm UTC](https://discourse.cmake.org/t/building-mpich-as-an-external-project-results-in-an-odd-fortran-error-fcmodoutflag-not-detected/927/1 "2020-04-02T14:58:58Z")

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I’m building several packages of scientific software, for use in my program, and for the life of me, I can’t figure out the behavior I’m seeing. I am unsure that it’s a bug, per se, but something is awry, and I’m not sure where to pin the problem.

One of the packages I’m building is MPICH. I’m using the externalproject\_add functionality, and this has typically worked, until recently. I’m building a host of other libraries with it - zstd, zlib, cgal, lib3ds, etc… some before, some after. I’ve used add\_dependencies to manage the order in which they should be built, as opposed to using DEPENDS directly inside the externalproject\_add function, as some of these may or may not be compiled, depending on what is found on a system.

If I build MPICH first, everything goes smooth. IE  
$ make -j MPICH && make

however, if I just use  
$make -j

I get an odd Fortran error in MPICH’s configure log - FCMODOUTPUTDIR not detected.

It seems that either MPICH’s configure script can’t figure out the -J flag from gcc when the build order is changed.

Any thoughts on how to track this down?

System: CentOS 7 x64  
Compilers: Developer Toolset {6,7,8,9} (gcc 6.X, 7.X, 8.X 9.X)  
CMake: 3.13 - 3.17  
MPICH: 3.2.1  
Make: 4.2.1

Edit: The relevant MPICH section

> ```
> ExternalProject_Add(MPICH
> URL ${CMAKE_CURRENT_SOURCE_DIR}/@canonical_name@
> URL_MD5 @package_md5@
> PREFIX ${CMAKE_CURRENT_BINARY_DIR}/MPICH
> INSTALL_DIR ${CMAKE_INSTALL_PREFIX}
> UPDATE_COMMAND
> #./autogen.sh
> CONFIGURE_COMMAND 
> ./configure 
> --prefix=<INSTALL_DIR>
> --enable-fast=all
> --enable-fortran=yes
> --enable-cxx=yes
> --enable-threads=multiple
> --enable-static=no 
> --enable-shared=yes
> --enable-strict
> --enable-versioning
> --with-pm=hydra
> --with-sysroot=<INSTALL_DIR>
> BUILD_IN_SOURCE 1
> LOG_CONFIGURE 1
> LOG_BUILD 1
> LOG_INSTALL 1
> TEST_COMMAND ""
> TEST_BEFORE_INSTALL 0
> TEST_EXCLUDE_FROM_MAIN 1
> )
> 
> ```

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<div class="post-metadata">

### Author: ![KBentley57](https://discourse.cmake.org/user_avatar/discourse.cmake.org/kbentley57/32/474_2.png) [@KBentley57](https://discourse.cmake.org/u/KBentley57)
#### Post date: [April 6, 2020, 3:29pm UTC](https://discourse.cmake.org/t/building-mpich-as-an-external-project-results-in-an-odd-fortran-error-fcmodoutflag-not-detected/927/2 "2020-04-06T15:29:58Z")

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Maybe this question is too specific. Generally, I think my question boils down to this -

Is there any reason CMake would modify the detected Fortran compiler during a configure / build, or, is there anything that would modify the internal dependencies?

Clearly, the ordering here matters, as the build succeeds when the build order is handled “manually”.

Thanks,

Kyle