1 files changed, 25 insertions, 2 deletions
diff --git a/comfignat.mk b/comfignat.mk
index 23e71aa..60c29b7 100644
--- a/comfignat.mk
+++ b/comfignat.mk
@@ -119,6 +119,13 @@ stagedir = ${builddir}/stage
 # installed are written under stagedir, and then copied to their destination in
 # the installation step.
 
+ifneq (${Comfignat_overriding_absolute_builddir},)
+   # This process is a sub-Make and must use the same builddir as its parent.
+   # This assignment must be done before builddir is used in VPATH and in the
+   # pathname of the configuration file.
+   override builddir := ${Comfignat_overriding_absolute_builddir}
+endif
+
 # Containing makefiles should avoid modifying the directory variables. Users
 # should be able to rely on these defaults.
 
@@ -264,19 +271,35 @@ configuration = ${builddir}/comfignat_configuration.mk
 ifeq (${origin builddir},command line)
    override builddir := ${abspath ${builddir}}
 endif
-ifeq (${origin objdir},command line)
+export Comfignat_overriding_absolute_builddir := ${builddir}
+
+ifneq (${Comfignat_overriding_absolute_objdir},)
+   override objdir := ${Comfignat_overriding_absolute_objdir}
+else ifeq (${origin objdir},command line)
    override objdir := ${abspath ${objdir}}
+   export Comfignat_overriding_absolute_objdir := ${objdir}
    objdir_is_overridden = true
 endif
-ifeq (${origin stagedir},command line)
+
+ifneq (${Comfignat_overriding_absolute_stagedir},)
+   override stagedir := ${Comfignat_overriding_absolute_stagedir}
+else ifeq (${origin stagedir},command line)
    override stagedir := ${abspath ${stagedir}}
+   export Comfignat_overriding_absolute_stagedir := ${stagedir}
    stagedir_is_overridden = true
 endif
+
 # These pathnames need to be absolute in project files, because a pathname
 # relative to a project file can be wrong when a separate build directory is
 # used and project files are both in srcdir and in builddir. objdir and
 # stagedir also need to be absolute in the configuration file because the
 # working directory might change between Make invocations.
+# Sub-Makes must use the same builddir, objdir and stagedir as the parent, so
+# the absolute pathnames are conveyed to child processes in environment
+# variables that won't normally be overridden and are unlikely to be defined by
+# accident.
+# The changes to objdir and stagedir must be done after the configuration file
+# is read because otherwise the configuration would override the command line.
 # Once modified the variables are no longer of command line origin, so they are
 # marked as overridden so that "make configure" will save them.