note that the topic was "gcc _with_pipes_"... the main reason to include the xargs examples was to get filenames from a pipe into gcc....
granted, -exec + is more elegant than xargs (and its in posix, says the manpage).
using xargs for building a single binary (the -o case) is a really bad idea anyway, as it will break in funny ways if you have too many files...
also, removing the --no-run-if will get you an error if there are no .c files to compile... (a rather useful gnu extension... at least gcc prints a reasonable error message for the empty argument list case - most programs resort to their help text, which causes confusion and/or havoc, depending on the text ending up on the terminal or in a pipe to another program)