To end 2015, I decided to finally learn C, instead of making it a 2016 resolution! I had previously done the ‘Learn C The Hard Way’ tutorials, taken about a year off, and thus forgotten everything.
Rather than re-do the same material, I decided to get ’21st Century C’ from O’Reilly and work through that. Unfortunately, there is an error/misprint in the very beginning chapters that makes doing the exercises near impossible on OSX. This error manifests itself as
c99: invalid argument 'all' to -W Error 64. If you encounter this error on OSX (I’m using OSX 10.11.2 El Capitan as of writing this post), here are three methods for fixing the issue.
When the discussion of using Makefiles begins on page 15, there is a discussion of the “smallest practicable makefile”, which is just six lines long:
1 2 3 4 5 6 7 P=program_name OBJECTS= CFLAGS= -g -Wall -O3 LDLIBS= CC=c99 $(P): $(OBJECTS)
Unfortunately, this doesn’t quite work on OSX. Page 11 in the book sort-of references that a fix is needed, but the directions aren’t so clear…
Error 64, solution 1: Book Fix, updated
To use the book fix, you are supposed to:
- Create a file named c99
- Put the lines
gcc -std=c99 $\*OR
clang $\*in the c99 file
- Add the file to your PATH in Terminal (such as
export PATH="/Users/computeruser:$PATH"if the
c99file were located in
chmod +x c99on the file to make it executable
Once you add this work-around to your PATH, then open a fresh Terminal window (or run
source .bash_profile to refresh the Bash settings), you should be able to use Make to compile your C code.
But to be honest, this seems like a really weird “fix” to me, as it overrides the C compiler settings for any program run via Terminal. I prefer one of two alternate solutions.
Error 64, solution 2: Makefile Change
As I was researching this, a helpful Twitter user noted:
@randyzwitch Remove space between CFLAGS and =, and replace c99 with cc. See man c99, -W is not -Wwarnings.
— Eugene Teo (@datajottings) December 30, 2015
When you switch the ‘c99’ reference to just ‘cc’ in the Makefile, everything works fine. Here’s the subtlety different, corrected Makefile:
1 2 3 4 5 6 7 P=program_name OBJECTS= CFLAGS= -g -Wall -O3 LDLIBS= CC=cc $(P): $(OBJECTS)
Error 64, solution 3: Switch to Clang
The final solution I came across is rather than using the GCC compiler, you can use an alternate compiler called Clang, which is also generally available on OSX (especially with XCode installed). Like solution 2 above, the Makefile is just subtlety different:
1 2 3 4 5 6 7 P=program_name OBJECTS= CFLAGS= -g -Wall -O3 LDLIBS= CC=clang $(P): $(OBJECTS)
Whether to use GCC or Clang as your compiler is really beyond the scope of this blog post; as 21st Century C discusses, it really shouldn’t matter (especially when you are just learning the mechanics of the language).
Error 64, Be Gone!
There’s not really much more to say at this point; this blog post is mainly documentation for anyone who comes across this error in the future. I’ve continued on through the book using Clang, but suffice to say, it’s not the compiler that writes poor-quality, non-compiling code, it’s the user. Ah, the fun of learning 🙂