Why does Make automatically execute a cc command?

I'm trying to learn how to use Make! So I have this simple Makefile,

all: main other

main: main.c other.o
    gcc main.c -o main
    echo "Compiled main.exe"

other: other.o

other.c:
    touch $@
    echo "int main(){return 0;}" > $@
    echo "Created other.c"

other.o: other.c
    gcc other.c -o other.o
    echo "Compiled other.o"

clean:
    rm -f main.exe other.o other.c

where everything executes as expected except at the end where a cc compile command is executed. Here is the output (I added the arrow),

> make all  
touch other.c
echo "int main(){return 0;}" > other.c
echo "Created other.c"
Created other.c
gcc other.c -o other.o
echo "Compiled other.o"
Compiled other.o
gcc main.c -o main
echo "Compiled main.exe"
Compiled main.exe
cc   other.o   -o other     <---
/usr/lib/gcc/x86_64-pc-msys/13.2.0/../../../../x86_64-pc-msys/bin/ld: other.o: in functio
n `mainCRTStartup':
/c/S/B/src/msys2-runtime/winsup/cygwin/crt0.c:20: multiple definition of `mainCRTStartup'
; /usr/lib/gcc/x86_64-pc-msys/13.2.0/../../../crt0.o:/c/S/B/src/msys2-runtime/winsup/cygw
in/crt0.c:20: first defined here
/usr/lib/gcc/x86_64-pc-msys/13.2.0/../../../../x86_64-pc-msys/bin/ld: other.o: in functio
n `mainCRTStartup':
/c/S/B/src/msys2-runtime/winsup/cygwin/crt0.c:20: multiple definition of `WinMainCRTStart
up'; /usr/lib/gcc/x86_64-pc-msys/13.2.0/../../../crt0.o:/c/S/B/src/msys2-runtime/winsup/c
ygwin/crt0.c:20: first defined here
/usr/lib/gcc/x86_64-pc-msys/13.2.0/../../../../x86_64-pc-msys/bin/ld: other.o:cygming-crt
beg:(.text+0x50): multiple definition of `__gcc_register_frame'; /usr/lib/gcc/x86_64-pc-m
sys/13.2.0/crtbegin.o:cygming-crtbeg:(.text+0x0): first defined here
/usr/lib/gcc/x86_64-pc-msys/13.2.0/../../../../x86_64-pc-msys/bin/ld: other.o:cygming-crt
beg:(.text+0x70): multiple definition of `__gcc_deregister_frame'; /usr/lib/gcc/x86_64-pc
-msys/13.2.0/crtbegin.o:cygming-crtbeg:(.text+0x20): first defined here
/usr/lib/gcc/x86_64-pc-msys/13.2.0/../../../../x86_64-pc-msys/bin/ld: other.o:cygming-crt
beg:(.data+0x0): multiple definition of `__dso_handle'; /usr/lib/gcc/x86_64-pc-msys/13.2.
0/crtbegin.o:cygming-crtbeg:(.data+0x0): first defined here
collect2: error: ld returned 1 exit status
make: *** [<builtin>: other] Error 1

Where the "<---" points to is the line in question. Why is this getting executed?

Solution

The problem is that the default program to build and link programs is cc. And with the rule other: other.o you tell make to build the executable other from the object file other.o which it will then do using the default linker.

And the errors are because gcc other.c -o other.o builds an executable program file named other.o. To build an object file you need to use the -c option.

The simple solution to all your problems, really, is to set the CC and LD variables, and rely on implicit rules to build your code.

Such a Makefile could look something like this:

# Explicitly use gcc as the compiler and linker
CC = gcc
LD = gcc

# The "default" target, because the first target in the makefile
# is what make will use when no target is specified
default: main other

# Build the main executable program from the main.c source
main: main.c

# Build the other executable program from the other.c source
other: other.c

# Create the other.c source file
other.c:
    echo "int main(){return 0;}" > $@

# The clean target isn't for creating a "clean" file, it's phony, fake
.PHONY: clean
clean:
    -rm -f main other other.c

_{[Please note that you need to convert the indentation to tabs]}