Makefile -std = c99错误

Question

all: matrices.c calculations.o
    gcc -std=c99 matrices.c calculations.o -o -lm PROGRAM2_EXE

lib: matrices.h calculations.c  
    gcc -c -std=c99 calculations.c -o calculations.o

clean: 
    rm matrices.o calculations.o PROGRAM2_EXE

This is my makefile for my project. Inside my matrices and my calculations.c there are multiple for loops. The error it gives me is error: 'for' loop initial declarations are only allowed in c99 mode but i have my -std=c99 in my file. My questions is

1. How do i fix my makefile to run with the for loops?

Answer 1

You don't have a rule for calculations.o . That means that the makefile does not specify how to generate calculations.o . You only have a rule for generating all and lib .

Gmake has some default rules. One of them is that if you do not have a rule for filename.o then it is compiled using $(CC) $(CPPFLAGS) $(CFLAGS) -c filename.c .

Your make all line is:

all: matrices.c calculations.o

When you issue make or make all , gmake checks the dependencies first. matrices.c already exists so that's fine. But if calculations.o does not exist, then it decides it needs to build calculations.o . You didn't specify a rule for calculations.o , so the implicit rule is used, which doesn't have -std=c99 in it.

Note that your lib rule is badly written. All rules should either create a file of the corresponding name, or be declared as .PHONY . It seems as if you think that make should somehow deduce that it needs to do make lib if the calculations.o file does not exist, but that isn't how make works.

To fix your problem , just change lib: to calculations.o: . Also, it would be good style to fix the all line. The rule does not make all , it makes PROGRAM2_EXE , so:

.PHONY: all
all: PROGRAM2_EXE

PROGRAM2_EXE: matrices.c calculations.o
    gcc -std=c99 matrices.c calculations.o -o PROGRAM2_EXE -lm

(Edit: as Chris Dodd points out, the -o switch must be immediately followed by the filename)

It would be better style to have a rule matrices.o that compiles matrices.c , and then a rule PROGRAM2_EXE: matrices.o calculations.o that links the two.

Answer 2

This action:

gcc -std=c99 matrices.c calculations.o -o -lm PROGRAM2_EXE

is telling gcc to produce an executable called -lm , which is probably not what you want.

Since you have no rule to produce connections.o , make will use its default rule to build it from connections.c , which is likely something like (from gmake):

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

Since you don't set -std=c99 in CFGLAGS or CPPFLAGS , it won't be used.

Answer 3

I use the following CFLAGS:

CFLAGS = -Wall -g -std=c99

It works very good for me.