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This page is intended to summarize the various compiler flags that we will be learning throughout the semester. There are hundreds (if not thousands!) of such options; we’ll only be dealing with a few of them.
These flags are for the clang compiler, but the are mostly the same for the g++ compiler (the only difference, of the ones listed below, are the flags to generate the particualr assembly flavor).
-O2: Creates an optimized executable. Note that if you
are using the -c command (below), then you should call -O2 for those as
well as the final linker call.-c <filename.cpp>: This flag will compile BUT NOT
LINK the passed .cpp file. It will create a filename.o file. To create
the executable, you must call the compiler with all the .o files
(i.e. clang *.o)-o <filename>: This will save the output
executable into clang -o foo foo.cpp will compile the foo.cpp file
and name the executable ‘foo’. If you do out specify this flag, the
output is saved to a.exe (or a.out in Linux/Unix). The ‘o’ in
-o stands for output (as in output file).-g: Include debugging information in the executable
file. This is needed to debug the file in gdb.-Wall: Display all warning messages. An error will
prevent the program from being compiled, whereas a warning will not.
There are many types of warnings that can be displayed, some of which
are rather obscure. The ‘all’ part means to display all of them. It is a
good idea to use this, as warnings are often bugs in your program.-S: generate assembly output, and then stop (i.e. does
not compile the program beyond the x86 assembly). Note that the assembly
format that is created as a result of this flag has a different format
than what we have seen in lecture – the idea is the same, but the
register specification is different, and the destination/source order is
reversed for the commands.-mllvm --x86-asm-syntax=intel: sets the assembly output
format to the flavor that we are used to in (this is the only flag on
this list that is not the same in g++)-MM: generates dependencies in the format used in
MakefilesIf you want to see all of the clang options, enter man
clang at the Linux prompt. It’s quite a list!