Bug 2390464

Summary:	Meson no longer detects Fortran module dependencies
Product:	[Fedora] Fedora	Reporter:	Susi Lehtola <susi.lehtola>
Component:	meson	Assignee:	Zbigniew Jędrzejewski-Szmek <zbyszek>
Status:	NEW ---	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	unspecified
Version:	43	CC:	caitlinwhittaker, carl, igor.raits, kalevlember, pbonzini, suraj.ghimire7, wtaymans, zbyszek
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Hardware:	Unspecified
OS:	Linux
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Bug Blocks:	2385747

Description Susi Lehtola 2025-08-22 20:33:54 UTC

The builds of xtb have started to fail. The error is

../src/prog/argparser.f90:20:8:
   20 |    use xtb_mctc_accuracy, only : wp
      |        1
Fatal Error: Cannot open module file ‘xtb_mctc_accuracy.mod’ for reading at (1): No such file or directory
compilation terminated.

xtb is built using meson and ninja. The missing file ‘xtb_mctc_accuracy.mod’ is generated from xtb/src/mctc/accuracy.f90, which means that meson/ninja is no longer handling this dependence correctly.

Reproducible: Always

Steps to Reproduce:
try to rebuild xtb package
Actual Results:
package fails to build

Expected Results:
package builds

Comment 1 Zbigniew Jędrzejewski-Szmek 2025-09-14 14:53:25 UTC

Hmm, I haven't used the fortran support in meson, but looking at the files, the
dependency just doesn't seem to be declared:

xtb_exe = executable(sources: prog, dependencies: xtb_dep_static, …)
xtb_dep_static = declare_dependency(link_with: xtb_common, …)
xtb_common = get_option('default_library') == 'both' ? xtb_lib.get_static_lib() : xtb_lib
xtb_lib = library(srcs, …)

So srcs has to be processed before the linking phase of xtb_exe, but
nothing indicates that it needs to be processed before the compilation step
of xtb_exe.

https://github.com/mesonbuild/meson/pull/12539 looks like it could be related.
But looking at the patches in that series, I see:

    # Fortran is a bit weird (again). When you link against a library, just compiling a source file
    # requires the mod files that are output when single files are built. To do this right we would need to
    # scan all inputs and write out explicit deps for each file. That is too slow and too much effort so
    # instead just have a full dependency on the library. This ensures all required mod files are created.

So it seems that the intent was to automatically handle the dependency,
contrary to what I wrote above.

Paolo, any idea about this? I think the first question is whether the xtb
config is correct or if it justed worked by accident previously…

The build works with the following workaround:
---------------&<--------------------------------------------------------------------------
diff --git xtb.spec xtb.spec
index abb57d2d21..7a9c1c7c4f 100644
--- xtb.spec
+++ xtb.spec
@@ -87,6 +87,7 @@ character(len=*),parameter :: version = "%{version}-%{release}%{dist}"
 character(len=*),parameter :: date = "$date"
 character(len=*),parameter :: author = "Fedora project"
 EOF
+ninja -C %{_vpath_builddir} -j %{_smp_build_ncpus} %{?__meson_verbose:--verbose} libxtb.a
 %meson_build

 %install
--------------->&--------------------------------------------------------------------------

Comment 3 Paolo Bonzini 2026-08-25 07:06:34 UTC

Another workaround, that shows how this is supposed to work:

$ ninja libxtb.so.6.7.1.p/depscan.json
$ sed 's/so\.6\.7\.1/a/' libxtb.so.6.7.1.p/depscan.json > libxtb.a.p/depscan.json
$ ninja

The build.ninja rule for libxtb.a.p/depscan.json has no dependencies. I'll report the issue upstream.