CODEWITHSUNDEEP
gccmakefilegnu-make
yuri kilochek
yuri kilochek

Reputation: 13486

GNU make unexpected behaviour

I want make to build all .cpp in the directory with tracking header changes. I attempt to do it by first making gcc output a target with dependencies with -MM option and then append the body to that target that will actually call the compilation:

OPTIONS = -std=c++11 -Wall

export

all : $(patsubst %.cpp, %.o, $(wildcard *.cpp))


%.o : %.mkt
    make -f $*.mkt

%.mkt : %.cpp
    gcc $(OPTIONS) -MM $*.cpp > $&.mkt1
    echo gcc $(OPTIONS) -c %.cpp > $*.mkt2
    cat $*.mkt1 $*.mkt2 > $*.mkt

Yet somehow this script issues the calls of the form

g++ -c -o something.o something.cpp

for each .cpp file in the directory. The temporary files .mkt1, .mkt2 and .mkt are not created. Why does this happen? How do i achive desired behaviour? I'm doing this on windows with mingw.

Upvotes: 0

Views: 128

Answers (1)

Beta
Beta

Reputation: 99094

You have supplied a chain of two pattern rules (%.cpp->%.mkt, %.mkt->%.o), but Make already has a single implicit rule (%.cpp->%.o) which it will find first, when searching for a way to build something.o.

The simplest way to solve the problem is to use make -r (or make --no-builtin-rules) which will disable the built-in implicit rule.

Upvotes: 2

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