Message-ID: <3952DB31.726CAD4F@pacbell.net>
From: Wesel <nospam AT pacbell DOT net>
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Subject: Make file wildcards
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Date: Thu, 22 Jun 2000 20:36:17 -0700
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

I'm sure this topic has gone around before, and I apologise for not
lurking long.  I have a question about the format of a makefile I was
hoping (praying?) that you might be able to help me with.

The makefile suggested by the good people at delorie.com went as
follows:
--------------------------------------------------------
CC = gcc
CFLAGS = -g -O2
OBJECTS = main.o foo.o

main.exe : $(OBJECTS)
        $(CC) $(CFLAGS) $(OBJECTS) -o main.exe

%.o : %.c
        $(CC) $(CFLAGS) -c $<
--------------------------------------------------------

The rule that stated %.o : %.c was supposed to happen whenever a file
with the extension .c got modified.  Taking this knowledge to heart, I
proceeded to make a single source file test.cpp.  I built my makefile as
follows:

--------------------------------------------------------
CC = gcc
CFLAGS = -g
OBJECTS = test.o

main.exe : $(OBJECTS)
	$(CC) $(CFLAGS) $(OBJECTS) -o main.exe

%.o : %.c %.cpp %.h
	$(CC) $(CFLAGS) -c $<
--------------------------------------------------------

My hopes were that upon discovering a modified .cpp file, make would
compile test.o then, finding a modified (created) test.o file, it would
build main.exe from the object file.  The makefile compiled fine, but it
used a sneaky implicit rule.  Apparantly %.o : %.cpp is built-in, so
what I saw was

--------------------------------------------------------
make -k
gpp    -c -o test.o test.cpp
gcc -g test.o -o main.exe

Compilation finished at Thu Jun 22 20:29:34
--------------------------------------------------------

One might notice that the implicit rule generates NO debug information
for test.o.  When I ran gdb on main.exe, it found no information about
line numbers, and couldn't show me the related source code.  Upon
disabling implicit rules, make returned with an error stating that a
rule for test.o was missing.

Why didn't "%.o : %.c %.cpp %.h" generate a rule for compiling test.o? 
Is there any way I can use wildcards with the make utility provided by
djgpp?  Do I have to write out every rule for every object-source pair I
use?  I do intend to have more than one source file eventually.

Thank you kindly.


Wesel

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