Makefile - make finds a file whilst shell does not - linux

Question

I've written a snippet of Makefile that checks if file exists before executing rm upon it.
clean:
echo "Attempt to remove $(exec) file"
if test -f "${exec}" ; then \
echo "Removing file ${exec}" ; \
rm ${exec} ; \
else \
echo "No ${exec} file to remove" ; \
fi
if "$(wildcard *.o)" = "" ; then \
echo "No files found" ; \
else \
echo " Found $(wildcard *.o) " ; \
fi
First if statement works fine
Attempt to remove hello file
No hello file to remove
while the second produces this:
/bin/sh: 1: main.o factorial.o: not found
Found main.o factorial.o
My question is: How come that make recipe produces valid output ( these files truly exist ) whilst the shell does not? And why shell even tries to find them?
Thank you for your time reading this question. That's my first one here so if I did something inappropriately please let me know

Answer 1

if main.o is very different than if test -f main.o. The former attempts to run a command main.o, while the latter runs the command test. if "main.o factorial.o" is similar, in that it attempts to run a command named main.o factorial.o which the shell is correctly complaining that it cannot find. It is not likely that you have a file named main.o factorial.o (that's a single file with a space in its name) in your PATH.
But don't do this. There is absolutely no point in ever checking whether or not a file exists before you unlink it. There's an inherent race condition. Just attempt to remove the file, and deal with errors that may occur if the file didn't exist.
It's much easier to write rm $(wildcard *.o) and just let rm emit error messages for files that don't exist. Or rm -f $(wildcard *.o) to suppress errors. If you really insist on iterating over the files and checking, you could do something like:
for f in $(wildcard *.o); do \
if ! test -f "$$f"; then echo "$$f" does not exist; \
else rm "$$f"; fi
but it's really not worth it. Also, it seems pretty pointless since the wildcard is only going to expand to files that exist. (But note that this exhibits the same race condition: the wildcard might expand to a list of files, but new files might be created between the time the wildcard is expanded and the rm is run.) Don't use wildcard like this. Explicitly list the files that you want to work with.