multiple definition of <function> - c

/tmp/ccTQFVCP.o: In function `whiteSpace':
/home/tommo/fly/flyc/config.c:12: multiple definition of `whiteSpace'
/tmp/cc0ccMfz.o:/home/tommo/fly/flyc/config.c:12: first defined here
/tmp/ccTQFVCP.o: In function `lineEnd':
/home/tommo/fly/flyc/config.c:16: multiple definition of `lineEnd'
/tmp/cc0ccMfz.o:/home/tommo/fly/flyc/config.c:16: first defined here
/tmp/ccTQFVCP.o: In function `makeSubStr':
/home/tommo/fly/flyc/config.c:20: multiple definition of `makeSubStr'
/tmp/cc0ccMfz.o:/home/tommo/fly/flyc/config.c:20: first defined here
I'm getting this for every function in my file config.c
Every one of my header files has a #ifndef FILE_H header block thing.
Why is it doing this?
TARGET = fly
SRC = main.c gfx.c transform.c entity.c list.c v3.c config.c airplane.c
CPPFLAGS = -Wall
LDFLAGS = -lglfw -lGL -lGLU
DEBUG = -g
linux:
#echo Building for Linux...
gcc $(CPPFLAGS) $(DEBUG) $(LDFLAGS) $(SRC) -o $(TARGET)
#echo All done.
clean:
rm $(TARGET)
help:
#echo "Available targets for fly"
#echo " linux: build for linux (default)"
#echo " clean: clean up directory"
.PHONY: help clean
That's my Makefile. git pull from https://github.com/tm1rbrt/fly If you wanna try to build yourself

The problem is this: main.c includes config.c. As a consequence, you get everything in config.c twice. It's unconventional that C files include each other, so I recommend to drop the include.

I faced a similar issue, I was wrong including the application.cpp file in the main.cpp, after changing it to application.hpp it fixed the issue.

Related

How to stop Make from recompiling the whole project if one include file changes? [duplicate]

I have the following makefile that I use to build a program (a kernel, actually) that I'm working on. Its from scratch and I'm learning about the process, so its not perfect, but I think its powerful enough at this point for my level of experience writing makefiles.
AS = nasm
CC = gcc
LD = ld
TARGET = core
BUILD = build
SOURCES = source
INCLUDE = include
ASM = assembly
VPATH = $(SOURCES)
CFLAGS = -Wall -O -fstrength-reduce -fomit-frame-pointer -finline-functions \
-nostdinc -fno-builtin -I $(INCLUDE)
ASFLAGS = -f elf
#CFILES = core.c consoleio.c system.c
CFILES = $(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.c)))
SFILES = assembly/start.asm
SOBJS = $(SFILES:.asm=.o)
COBJS = $(CFILES:.c=.o)
OBJS = $(SOBJS) $(COBJS)
build : $(TARGET).img
$(TARGET).img : $(TARGET).elf
c:/python26/python.exe concat.py stage1 stage2 pad.bin core.elf floppy.img
$(TARGET).elf : $(OBJS)
$(LD) -T link.ld -o $# $^
$(SOBJS) : $(SFILES)
$(AS) $(ASFLAGS) $< -o $#
%.o: %.c
#echo Compiling $<...
$(CC) $(CFLAGS) -c -o $# $<
#Clean Script - Should clear out all .o files everywhere and all that.
clean:
-del *.img
-del *.o
-del assembly\*.o
-del core.elf
My main issue with this makefile is that when I modify a header file that one or more C files include, the C files aren't rebuilt. I can fix this quite easily by having all of my header files be dependencies for all of my C files, but that would effectively cause a complete rebuild of the project any time I changed/added a header file, which would not be very graceful.
What I want is for only the C files that include the header file I change to be rebuilt, and for the entire project to be linked again. I can do the linking by causing all header files to be dependencies of the target, but I cannot figure out how to make the C files be invalidated when their included header files are newer.
I've heard that GCC has some commands to make this possible (so the makefile can somehow figure out which files need to be rebuilt) but I can't for the life of me find an actual implementation example to look at. Can someone post a solution that will enable this behavior in a makefile?
EDIT: I should clarify, I'm familiar with the concept of putting the individual targets in and having each target.o require the header files. That requires me to be editing the makefile every time I include a header file somewhere, which is a bit of a pain. I'm looking for a solution that can derive the header file dependencies on its own, which I'm fairly certain I've seen in other projects.
As already pointed out elsewhere on this site, see this page:
Auto-Dependency Generation
In short, gcc can automatically create .d dependency files for you, which are mini makefile fragments containing the dependencies of the .c file you compiled.
Every time you change the .c file and compile it, the .d file will be updated.
Besides adding the -M flag to gcc, you'll need to include the .d files in the makefile (like Chris wrote above).
There are some more complicated issues in the page which are solved using sed, but you can ignore them and do a "make clean" to clear away the .d files whenever make complains about not being able to build a header file that no longer exists.
You could add a 'make depend' command as others have stated but why not get gcc to create dependencies and compile at the same time:
DEPS := $(COBJS:.o=.d)
-include $(DEPS)
%.o: %.c
$(CC) -c $(CFLAGS) -MM -MF $(patsubst %.o,%.d,$#) -o $# $<
The '-MF' parameter specifies a file to store the dependencies in.
The dash at the start of '-include' tells Make to continue when the .d file doesn't exist (e.g. on first compilation).
Note there seems to be a bug in gcc regarding the -o option. If you set the object filename to say obj/_file__c.o then the generated _file_.d will still contain _file_.o, not obj/_file_c.o.
This is equivalent to Chris Dodd's answer, but uses a different naming convention (and coincidentally doesn't require the sed magic. Copied from a later duplicate.
If you are using a GNU compiler, the compiler can assemble a list of dependencies for you. Makefile fragment:
depend: .depend
.depend: $(SOURCES)
rm -f ./.depend
$(CC) $(CFLAGS) -MM $^>>./.depend;
include .depend
There is also the tool makedepend, but I never liked it as much as gcc -MM
You'll have to make individual targets for each C file, and then list the header file as a dependency. You can still use your generic targets, and just place the .h dependencies afterwards, like so:
%.o: %.c
#echo Compiling $<...
$(CC) $(CFLAGS) -c -o $# $<
foo.c: bar.h
# And so on...
Basically, you need to dynamically create the makefile rules to rebuild the object files when the header files change. If you use gcc and gnumake, this is fairly easy; just put something like:
$(OBJDIR)/%.d: %.c
$(CC) -MM -MG $(CPPFLAGS) $< | sed -e 's,^\([^:]*\)\.o[ ]*:,$(#D)/\1.o $(#D)/\1.d:,' >$#
ifneq ($(MAKECMDGOALS),clean)
include $(SRCS:%.c=$(OBJDIR)/%.d)
endif
in your makefile.
Over and above what #mipadi said, you can also explore the use of the '-M' option to generate a record of the dependencies. You might even generate those into a separate file (perhaps 'depend.mk') which you then include in the makefile. Or you can find a 'make depend' rule which edits the makefile with the correct dependencies (Google terms: "do not remove this line" and depend).
Simpler solution: Just use the Makefile to have the .c to .o compilation rule be dependent on the header file(s) and whatever else is relevant in your project as a dependency.
E.g., in the Makefile somewhere:
DEPENDENCIES=mydefs.h yourdefs.h Makefile GameOfThrones.S07E01.mkv
::: (your other Makefile statements like rules
::: for constructing executables or libraries)
# Compile any .c to the corresponding .o file:
%.o: %.c $(DEPENDENCIES)
$(CC) $(CFLAGS) -c -o $# $<
None of the answers worked for me. E.g. Martin Fido's answer suggests gcc can create dependency file, but when I tried that it was generating empty (zero bytes) object files for me without any warnings or errors. It might be a gcc bug. I am on
$ gcc --version gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-16)
So here's my complete Makefile that works for me; it's a combination of solutions + something that wasn't mentioned by anyone else (e.g. "suffix replacement rule" specified as .cc.o:):
CC = g++
CFLAGS = -Wall -g -std=c++0x
INCLUDES = -I./includes/
# LFLAGS = -L../lib
# LIBS = -lmylib -lm
# List of all source files
SRCS = main.cc cache.cc
# Object files defined from source files
OBJS = $(SRCS:.cc=.o)
# # define the executable file
MAIN = cache_test
#List of non-file based targets:
.PHONY: depend clean all
## .DEFAULT_GOAL := all
# List of dependencies defined from list of object files
DEPS := $(OBJS:.o=.d)
all: $(MAIN)
-include $(DEPS)
$(MAIN): $(OBJS)
$(CC) $(CFLAGS) $(INCLUDES) -o $(MAIN) $(OBJS) $(LFLAGS) $(LIBS)
#suffix replacement rule for building .o's from .cc's
#build dependency files first, second line actually compiles into .o
.cc.o:
$(CC) $(CFLAGS) $(INCLUDES) -c -MM -MF $(patsubst %.o,%.d,$#) $<
$(CC) $(CFLAGS) $(INCLUDES) -c -o $# $<
clean:
$(RM) *.o *~ $(MAIN) *.d
Notice I used .cc .. The above Makefile is easy to adjust for .c files.
Also notice importance of these two lines :
$(CC) $(CFLAGS) $(INCLUDES) -c -MM -MF $(patsubst %.o,%.d,$#) $<
$(CC) $(CFLAGS) $(INCLUDES) -c -o $# $<
so gcc is called once to build a dependency file first, and then actually compiles a .cc file. And so on for each source file.
I believe the mkdep command is what you want. It actually scans .c files for #include lines and creates a dependency tree for them. I believe Automake/Autoconf projects use this by default.

Makefile link issue

I can't figure out how link static libraries in Makefiles. I use ubuntu 20.04 LTS. I even tried to use direct path to these libraries, and the issue remains unchanged. Here's my Makefile code.
LIB = libgeoms.a
SRC = mlx_pxl_put.c \
std_arc.c \
std_crcl.c \
std_line.c \
std_poly.c \
std_rect.c \
CC = clang
WARNS = -Wall -Wextra -Werror
OBJ = $(SRC:.c=.o)
SRCP = /usr/local/wealdboar/src/
INCLUDEP = /usr/local/wealdboar/include/
LIBP = /usr/local/wealdboar/lib/
HEADER = geoms.h
LX11P = /usr/lib/x86_64-linux-gnu/libX11.a
LXEXTP = /usr/lib/x86_64-linux-gnu/libXext.a
LMLX = /usr/local/lib/libmlx.a
$(LIB): $(OBJ)
#echo "Every funtion is compile proved ..."
#ar rcs $(LIB) $(OBJ)
#echo "All functions added to static lib ..."
$(OBJ): %.o :%.c
#echo "check $< to be right"
#$(CC) $(WARNS) -c $(LX11P) $(LMLX) $(LXEXTP) $< -o $#
all: $(LIB)
clean:
#echo "removing all binaries ..."
#rm -rf $(OBJ)
fclean: clean
#echo "removing static library ..."
#rm -rf $(LIB)
re: fclean all
install: re clean
#echo "coping $(LIB) to $(LIBP)"
#sudo cp $(LIB) $(LIBP)
#echo "coping sources to $(SRCP)"
#sudo cp $(SRC) $(SRCP)
#echo "coping header to $(INCLUDEP)"
#sudo cp $(HEADER) $(INCLUDEP)
Issue image
You haven't specified the -l or -L flags to tell clang to link against choosen libraries.
First please don't paste image links in StackOverflow. They aren't searchable, they aren't quotable, and many people are not willing to click a on links to other sites. Please cut and paste the actual messages.
Second, when working with makefiles you should not use the # option which hides the most important information about the commands being run. It's much harder to debug a makefile when the command lines are not visible. If you really want to hide the actual commands you should either add in the # after everything is already working and not before, or else use tricks like this to allow for a debug mode.
Finally your error is as I suggested in my comment above. You are trying to add static libraries to a compile command (a command that compiles source files into object files). Libraries can only be added into link commands (commands that convert object files and libraries into executables).
You are not actually creating an executable anywhere in your makefile that I can see, so there's nowhere that you can add libraries here. But, you need to remove them from the compile rule:
$(OBJ): %.o :%.c
#echo "check $< to be right"
#$(CC) $(WARNS) -c $< -o $#

Makefile dependencies on multiple files

I have created a Makefile for unit tests which uses GCC with arguments to create profiling files (gcno) during compiling. Here's a similified part of it where compiling and linking takes place:
UTEXE = $(UTOBJSDIR)\$(UTUNIT).exe
UTOBJS = $(UTUUTSRC:.c=.o) $(UTUTSRC:.c=.o) $(UTCSRC:.c=.o)
UTOBJSFULL = $(addprefix $(UTOBJSDIR)\,$(UTOBJS))
UTOBJSGCNO = $(addprefix $(UTOBJSDIR)\,$(UTOBJS:.o=.gcno))
$(UTOBJS): %.o: %.c $(UTMAKEDEP)
$(call report,Compiling $(*F).c)
$(MKDEP) $(MKDFLAGS) -o.o -f$(UTOBJSDIR)\$(*F).dep $(subst /,\,$<)
$(CC) -c $(CFLAGS) $(subst /,\,$<) -o $(UTOBJSDIR)/$#
$(UTOBJSGCNO): $(UTOBJS) $(UTMAKEDEP)
utbuild: $(UTEXE) $(UTOBJSGCNO) $(UTOBJS) $(UTMAKEDEP)
$(UTEXE): $(UTOBJSGCNO) $(UTOBJS) $(UTMAKEDEP)
$(call report,Linking to $(UTUNIT).exe)
$(LINK) $(UTOBJSFULL) $(LNKFLAGS) -o $(UTEXE)
It compiles all the object and profile files and links together a binary. However when i delete some profile file (gcno) and call "utbuild" again it won't re-compile to restore the .gcno file. It tries to do linking again because gcno is a prequisite to it, but it wont do the compiling.
I don't know how to name this case so couldn't find solution from internet. Basically one recipe creates two files and i don't know how to write the rule that re-run's recipe even when only one file needs to re-created.
I would appreciate some links or hints.
thanks for all the comments. I've tried no-op ";" and ":=" with same outcome.
I think i need to take one step back and explain why i asked this question. It's not just about deleting or not-deleting gcno files manually, it's about general understanding how to write such a Makefile which restores any missing or out-of-date file. My Makefile has similar cases in few places and it's using parallel build so when some file goes missing it gives lot of weird errors. Usually it's solved by "clean" and "all", but i'd like the Makefile to be perfect and handle the missing file issues nicely.
As the example above is not so clear without all the rest of the Makefile then i made a new simple test.
hello.c
#include <stdio.h>
int main()
{
printf("Hello world\n");
}
Makefile
CCDIR = C:\tools\MinGW
CCBINDIR = $(CCDIR)\bin
CCINCDIR = $(CCDIR)\include;$(CCDIR)\lib\gcc\mingw32\4.8.1\include
CCLIBDIR = $(CCDIR)\lib;$(CCDIR)\lib\gcc\mingw32\4.8.1
# Overcome "missing dll file" messages on Windows
CC = set PATH=%PATH%;$(CCBINDIR)& $(CCBINDIR)\gcc.exe
LINK = set PATH=%PATH%;$(CCBINDIR)& $(CCBINDIR)\gcc.exe
# Compile and link for code coverage
CFLAGS = -fprofile-arcs -ftest-coverage -g3 -O0 $(addprefix -I,$(CCINCDIR))
LNKFLAGS = -fprofile-arcs -ftest-coverage -static -static-libgcc $(addprefix -L,$(CCLIBDIR))
OBJECTS = hello.o
EXE = hello.exe
$(OBJECTS): %.o: %.c
$(CC) -c $(CFLAGS) $(subst /,\,$<) -o $#
$(EXE): $(OBJECTS)
$(LINK) $(OBJECTS) $(LNKFLAGS) -o $(EXE)
build: $(EXE)
"make build" creates following files:
hello.o
hello.gcno
hello.exe
Now if i delete the "hello.gcno" and run build again it tells me:
mingw32-make: Nothing to be done for 'build'.
The goal is to update Makefile so that the make re-creates the "hello.gcno". It would probably re-create "hello.o" and "hello.exe" also during that process but that's not a problem.
Edit:
Just to be clear: in real Makefile i really-really need the .gcno files. It's not just an additional information or something which to avoid or do optionally. The Makefile builds the unit test executables, runs them and executes gcov to generate code coverage information and gcovr creates a report of all the .gcov files. If .gcno file is missing it won't work. Also - as it's parallel build then dependencies shall be absolutely correct to avoid some process starting earlier and it's tricky because coverage report has dependencies coming from two "branches" - .gcno files from compile stage and .gcda files from execute stage. So that's why i need it to be correct.
your only option here is this :
(if you can change the rule)
$(EXE): $(OBJECTS)
$(LINK) $(OBJECTS) $(LNKFLAGS) -o $(EXE)
to this:
%.exe %.gnco: $(OBJECTS)
$(LINK) $(OBJECTS) $(LNKFLAGS) -o $(EXE)
$(GENERATE_GNCO) $<
Here is a very simple solution of one thing dependig on two other things
compile:./src/main.c ./src/error.c
gcc ./src/error.c ./src/main.c -o ./exe/calc
run : ./exe/calc
./exe/calc
The correct answer in my opinion, is, don't delete any .gcno files by themselves. If you have to "clean", use make clean, but don't just go about deleting files.
The "build" is a state machine, with all the files constituting a "state". Don't corrupt the state!
Some people say, one should be able to delete arbitrary files and the build should recover. My answer is, what about if you corrupt some .o file by hand, say, add some 0's and 1's, making it unusable (thank you user3629249 for pointing that needs to be clarified, that I am talking about corruption, not intentional editing). Should the build also recover from that? Obviously no - no build system in the world will recover if you touch the .o file this way. Then why allow deleting a file, but not allow modifying it?? Where do you draw the line?
Simply put, any corruption should not be allowed. Use make clean only, or better yet, write your Makefile properly, so you never need to clean period.
The whole Makefile has a number of problems, here is how it should look like (I am assuming this is on Windows/DOS):
.SUFFIXES:
UTEXE := $(UTOBJSDIR)\$(UTUNIT).exe
UTOBJSFULL := $(addprefix $(UTOBJSDIR)\,$(subst /,\, $(UTUUTSRC:.c=.o) $(UTUTSRC:.c=.o) $(UTCSRC:.c=.o)))
UTOBJSGCNO := $(UTOBJSFULL:.o=.gcno)
.PHONY: utbuild all
all: utbuild
utbuild: $(UTEXE) $(UTOBJSGCNO) $(UTMAKEDEP)
$(UTOBJSGCNO): %.gcno: %.o $(UTMAKEDEP) ;
.SECONDARY: %\.
%\.: Makefile
mkdir $*
.SECONDEXPANSION:
$(UTOBJSFULL): $(UTOBJSDIR)\%.o: %.c $(UTMAKEDEP) | $$(#D)\.
$(call report,Compiling $<)
$(MKDEP) $(MKDFLAGS) -o.o -f$(UTOBJSDIR)\$(*F).dep $<
$(CC) -c $(CFLAGS) $< -o $#
$(UTEXE): $(UTOBJSFULL) $(UTMAKEDEP) | $$(#D)\.
$(call report,Linking to $(#F))
$(LINK) $(UTOBJSFULL) $(LNKFLAGS) -o $#

What is wrong with this Makefile? (header files not found)

I am modifying an old makefile in order to build a C extension for postgreSQL. The Makefile currently looks like this:
PGLIB = /usr/lib/postgresql/8.4/lib
PQINC = /usr/include/postgresql/8.4/server
CC=gcc
override CFLAGS+= $(CFLAGS_SL) -DPG_AGGREGATE
SHLIB = pg_myextlib
SRC = foo.c \
foobar.c
OBJS = foo.o \
foobar.o
all: $(OBJS)
$(CC) -shared -o $(SHLIB)$(DLSUFFIX) $(OBJS) -I$(PQINC)
cp *.so $(PGLIB)
clean:
rm -f $(SHLIB) $(OBJS)
The error I get when I run make is:
common.h:58:22: error: postgres.h: No such file or directory
Which suggests that the include path is not being added (the file exists in $PQINC).
Its a long time since I wrote the Makefile - and I haven't written many since. As an aside, I am pretty sure that 'shared' is not the gcc flag to build shared libs on Ubuntu (my current dev box) - I think the flag should be 'fPIC' - can someone confirm this?
I am runing gcc v4.4.3 on Ubuntu 10.0.4 and compiling for use with PG 8.4
Try moving the -I$(PQINC) from target all to the end of line that starts with override CFLAGS.
Placing -Isomething on the compiler line which turns object files, like those in $(OBJS), into executable will have no effect whatsoever.
You need to do it when you compile the source files.
Since your makefile doesn't explicitly show the rule for processing source files, it may well be using a default one, which is incredibly unlikely to know about PQINC.
You seem to be using the default rules to build foo.o from foo.c, which doesn't have your -I. Try adding the following rule to your Makefile:
.c.o:
$(CC) $(CFLAGS) -c $< -o $# -I$(PQINC)

Why does this makefile not apply includes to all objects?

This makefile does not behave as I expect. I want it to build .o files for each .c file in the current directory and subdirectories, and put them in a static library. However, it stops applying my $(INCS) after the first or second file. When it tries to build the second .o file, I don't see the -I paths in the build line and it complains about not finding a header file therein. Names have been genericized to simplify things. I'm using cygwin on Windows XP. I'm using an ARM cross compiler that is not under the cygwin tree. I based this makefile off an answer here. There are only about two dozen .c files so the overhead of creating the dependency files this way isn't a big deal.
# Project specific options
CC = my-cross-gcc
INCS := -I. -Iinc
INCS += -Imy/inc/path
CFLAGS := -Wall -fPIC -static -cross-compiler-specific-options
OUT := bin/libmylib.a
MKDIR:=mkdir -p
### Generic C makefile items below:
# Add .d to Make's recognized suffixes.
SUFFIXES += .d
NODEPS:=clean
#Find all the C files in this directory, recursively
SOURCES:=$(shell find . -name "*.c")
#These are the dependency files
DEPFILES:=$(patsubst %.c,%.d,$(SOURCES))
OBJS:= $(patsubst %.c,%.o,$(SOURCES))
#Don't create dependencies when we're cleaning, for instance
ifeq (0, $(words $(findstring $(MAKECMDGOALS), $(NODEPS))))
-include $(DEPFILES)
endif
#This is the rule for creating the dependency files
%.d: %.c
$(CC) $(INCS) $(CFLAGS) -MM -MT '$(patsubst %.c, %.o,$(patsubst %.c,%.o,$<))' $< > $#
#This rule does the compilation
%.o: %.c %.d %.h
$(CC) $(INCS) $(CFLAGS) -o $# -c $<
# Now create a static library
all: $(OBJS)
#$(MKDIR) bin
ar rcsvq $(OUT) $(OBJS)
clean:
rm -rf $(OBJS) $(OUT) $(DEPFILES)
Why does this makefile not apply $(INCS) when building subsequent .o files? How do I fix it? Output resembles this:
$ make all
my-cross-gcc -I. -Iinc -Imy/inc/path -<compiler options> -o firstfile.o -c firstfile.c
my-cross-gcc -I. -Iinc -Imy/inc/path -<compiler options> -o secondfile.o -c secondfile.c
my-cross-gcc -<compiler flags> -o thirdfile.o -c thirdfile.c
thirdfile.c:23:18: fatal error: myinc.h: No such file or directory
compilation terminated.
When I go to the command line and type in the gcc line to build thirdfile.o and use the -I paths, the object file is successfully built.
There are two different mechanisms for handling header files at work here:
When the compiler is trying to build foo.o from foo.c, and in foo.c it encounters #include "foo.h", it goes looking for foo.h. The -I flags tell it where to look. If it is invoked without the flags it needs to find foo.h, it will complain and die.
When Make is trying to build foo.o, and considering which rule to use, it looks at the prerequisites. The prerequisites for your rule are foo.c foo.d foo.h, so it goes looking for those prerequisites. How is it to know where foo.h is? Note that the compiler flag inside one of its commands is of no use-- it won't make any deductions about that. If it can't find (and doesn't know how to make) a prerequisite, it will reject that rule and look for another one, such as the implicit %.o rule which knows nothing about your $(INCS) variable, and that leads you to the problem described above.
If this is the problem (and you can check by looking at the locations of the headers and doing some experiments) you have a couple of options:
A) You can use the implicit rule, and it's variables. Just add INCS to CFLAGS and you'll probably get the results you want. This tells the compiler what to do, but it still leaves Make in the dark about the dependencies, so you'll probably have to double-check that your dependency handling is correct.
B) You can tell Make where to find the header files:
vpath %.h inc my/inc/path
(You may notice that this is redundant with your INCS variable, and redundancy is bad-- you can eliminate this redundancy, but I urge you to get it working first.)
I'm going to guess that you have files named firstfile.h, secondfile.h, but no file named thirdfile.h?
I would then suppose that make cannot use the rule you gave it because and can't find or build the .h file. So it decides to use the default implicit rule instead.
All I can imagine is that for "thirdfile" your depfile is somehow out-of-date or corrupt. Perhaps it is bad enough that it's confusing make into calling some other default target.

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