# Cmake 3.27.8 regression with Ninja and Fortran dependencies
**URL:** https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920
**Category:** Usage
**Tags:** gen:ninja
**Created:** [January 24, 2024, 4:26pm UTC](https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920 "2024-01-24T16:26:42Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@krefson](https://discourse.cmake.org/u/krefson)
#### Post date: [January 24, 2024, 4:26pm UTC](https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920/1 "2024-01-24T16:26:42Z")
I think I found a regression with the dependency generation for Ninja in 3.27.8.
I am one of the developers of CASTEP, a large electronic structure code predominantly in Fortran. CMake builds with cmake 3.20.4 - 3.25.1 appear to work correctly when used with the Ninja backend.
However a user reports a build failure with cmake i 3.27.8 and Ninja 1.11.1 in parallel on the Darwin/macports which I reproduce under OpenSuSE linux. The system is attempting to compile one of the modules before a module on which it depends, and the compile fails because the .mod file it depends on has not yet been created.
I’ll emphasise that this is a regression in a previously-working and well-tested cmake build.
- Serial builds work, but parallel with “-j” fail.
- Builds with unix makefile backend always succeed in both serial and parallel. Ninja fails.
- cmake 3.25.1 and below generate working parallel builds with Ninja
- cmake 2.37.8 and 3.28.1 fail
- cmake 3.27.9 succeeds.
Any suggestions as to what might have changed and how to investigate further would be very welcome.
Keith Refson
---
### Author:  [@brad.king](https://discourse.cmake.org/u/brad.king)
#### Post date: [January 24, 2024, 7:16pm UTC](https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920/2 "2024-01-24T19:16:49Z")
Cc: @ben.boeckel
3.27 tried to make dependencies for Fortran and C++ modules more exact, but doing so exposed a parade of cases in which the “exact” dependencies were not correctly computed. [CMake MR 8996](https://gitlab.kitware.com/cmake/cmake/-/merge_requests/8996) reverted the change for 3.27.9 to stabilize the 3.27 series, but the 3.28 series continues the effort. See that MR for details.
Please try to narrow your use case down to a simple example, and open [an issue](https://gitlab.kitware.com/cmake/cmake/-/issues) to demonstrate the problem.
---
### Author:  [@krefson](https://discourse.cmake.org/u/krefson)
#### Post date: [January 29, 2024, 1:17pm UTC](https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920/3 "2024-01-29T13:17:15Z")
Ah thank you. This helped a lot to narrow down the issue. The missing dependency was for building an object library:
```auto
add_library(MY_OBJ_LIB OBJECT my_obj_lib.f90)
add_dependencies(MY_OBJ_LIB my-dep-lib)
```
The build was attempting to compile `my_obj_lib.f90` before any of the fortran files in `my-dep-lib`, and failing because the .mod file for the dependent libraries was missing. Curiously, changing the `add_dependencies` line to
```auto
target_link_libraries(MY_OBJ_LIB my-dep-lib)
```
puts the dependency back and the compile succeeds.
I’m yet to check whether a minimal example can be constructed to display this behaviour.
Keith Refson
---
### Author:  [@brad.king](https://discourse.cmake.org/u/brad.king)
#### Post date: [January 29, 2024, 3:07pm UTC](https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920/4 "2024-01-29T15:07:10Z")
If `MY_OBJ_LIB` depends on modules or symbols from `my-dep-lib`, then linking the latter via `target_link_libraries` is correct. `add_dependencies` is not enough, and worked only by accident before.
---
### Author:  [@krefson](https://discourse.cmake.org/u/krefson)
#### Post date: [January 30, 2024, 9:54am UTC](https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920/5 "2024-01-30T09:54:29Z")
Thanks. No bug report necessary in that case, and an easy fix to my CMakelist.txt.
How CMake handles a dependency on a generated Fortran module file is still opaque to me.
As a matter of curiosity, how might such a dependency have been specified before 3.12, when `target_link_libraries` was not available?
---
### Author:  [@brad.king](https://discourse.cmake.org/u/brad.king)
#### Post date: [January 31, 2024, 1:22pm UTC](https://discourse.cmake.org/t/cmake-3-27-8-regression-with-ninja-and-fortran-dependencies/9920/6 "2024-01-31T13:22:08Z")
Prior to 3.12, object libraries were referenced in `add_library` calls as sources by `$`. That also hooks up the dependencies.