Hello everyone! I am a casual Xcode user, mostly version 3, but switched to version 4 in December. I am taking a compiler writing course and our initial homework uses lex and yacc. From a terminal window I can compile the lex output file and execute it using: gcc lex.yy.c -ll The gcc being used is from: /Developer/usr/bin and is version i686-apple-darwin11-llvm-gcc-4.2 Putting the same file into an Xcode project and trying to compile it returns an Apple Mach-O Linker (ld) Error: ld: library not found for -ll Command /Developer/usr/bin/llvm-gcc-4.2 failed with exit code 1 I added the -ll link flag in the "Linking" area of the "Build Settings" under the "Other Linker Flags" option line and see it getting included in the gcc command line. I tried using both LLVM GCC 4.2 and Apple LLVM compiler 3.0 as the selected compiler in the "Build Options->Compiler" field. I also tried using -llibl rather than -ll, but that did not work either. I really want to be able to use Xcode for the assignments later in the course so I don't have to work directly with gdb. Any suggestions as to how to get Xcode to locate the lex and yacc libraries will be greatly appreciated!!!