problem with gnu Make in Makefile.manual

[fiolj]

When using a recent version of make: GNU Make 4.3 in linux.

Using the instructions:

make -f Makefile.manual FYPPFLAGS=-DMAXRANK=4

compilation fails because the variable FYPPFLAGS may not be modified after being set in the command line.
Details are given in override directive

A possible solution is to use a different variable name. I've solved it by making the following changes:

Makefile.manual     | 6 ++++--
src/Makefile.manual | 2 +-

modified   Makefile.manual
@@ -5,14 +5,16 @@ FFLAGS ?= -Wall -Wextra -Wimplicit-interface -fPIC -g -fcheck=all
 FYPPFLAGS ?=
 
 VERSION := $(subst ., ,$(file < VERSION))
-FYPPFLAGS += \
+VERS_FYPPFLAGS = \
              -DPROJECT_VERSION_MAJOR=$(word 1,$(VERSION)) \
              -DPROJECT_VERSION_MINOR=$(word 2,$(VERSION)) \
              -DPROJECT_VERSION_PATCH=$(word 3,$(VERSION))
 
+ALL_FYPPFLAGS := $(FYPPFLAGS) $(VERS_FYPPFLAGS)
+
 export FC
 export FFLAGS
-export FYPPFLAGS
+export ALL_FYPPFLAGS
 
 .PHONY: all clean test
 
modified   src/Makefile.manual
@@ -72,7 +72,7 @@ clean:
 	$(FC) $(FFLAGS) -c $<
 
 $(SRCGEN): %.f90: %.fypp common.fypp
-	fypp $(FYPPFLAGS) $< $@
+	fypp $(ALL_FYPPFLAGS) $< $@
 
 # Fortran module dependencies
 f18estop.o: stdlib_error.o

[awvwgk]

Thanks for sharing, do you mind opening a PR with your patch?

[fiolj]

Ok, some further test show that also makefiles in the tests directory must be modified in the same way. I can do that if there is consensus.
Alternatively, we can modify the command line with a different name for the variable. This way we only change the top directory makefile.manual but the instructions must be modified accordingly. The change to the makefile is small:

modified   Makefile.manual
@@ -2,14 +2,16 @@
 
 FC ?= gfortran
 FFLAGS ?= -Wall -Wextra -Wimplicit-interface -fPIC -g -fcheck=all
-FYPPFLAGS ?=
+ADD_FYPPFLAGS ?=
 
 VERSION := $(subst ., ,$(file < VERSION))
-FYPPFLAGS += \
+VERSION_FYPPFLAGS += \
              -DPROJECT_VERSION_MAJOR=$(word 1,$(VERSION)) \
              -DPROJECT_VERSION_MINOR=$(word 2,$(VERSION)) \
              -DPROJECT_VERSION_PATCH=$(word 3,$(VERSION))
 
+FYPPFLAGS := $(ADD_FYPPFLAGS) $(VERSION_FYPPFLAGS)
+
 export FC
 export FFLAGS
 export FYPPFLAGS

And in the README.md we must change the name of the variable:

modified   README.md
@@ -176,15 +176,15 @@ Alternatively, you can build using provided Makefiles:
 make -f Makefile.manual

-You can limit the maximum rank by setting -DMAXRANK=<num> in the FYPPFLAGS environment variable (which can reduce the compilation time):
+You can limit the maximum rank by setting -DMAXRANK=<num> in the ADD_FYPPFLAGS environment variable (which can reduce the compilation time):

-make -f Makefile.manual FYPPFLAGS=-DMAXRANK=4
+make -f Makefile.manual ADD_FYPPFLAGS=-DMAXRANK=4

You can also specify the compiler and compiler-flags by setting the FC and FFLAGS environmental variables. Among other things, this facilitates use of compiler optimizations that are not specified in the Makefile.manual defaults.

-make -f Makefile.manual FYPPFLAGS=-DMAXRANK=4 FC=gfortran FFLAGS="-O3 -flto"
+make -f Makefile.manual ADD_FYPPFLAGS=-DMAXRANK=4 FC=gfortran FFLAGS="-O3 -flto"

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