If you specify -g, and the optimization level is -xO3 or lower, the compiler provides best-effort symbolic information with almost full optimization. Tail-call optimization and back-end inlining are disabled.
If you specify -g and the optimization level is -xO4, the compiler provides best-effort symbolic information with full optimization.
Compile with the -g option to use the full capabilities of the Performance Analyzer. While some performance analysis features do not require -g, you must compile with -g to view annotated source, some function level information, and compiler commentary messages. See the analyzer(1) man page and the Performance Analyzer manual for more information.
The commentary messages that are generated with -g describe the optimizations and transformations that the compiler made while compiling your program. Use the er_src(1) command to display the messages, which are interleaved with the source code.
In previous releases, this option forced the compiler to use the incremental linker ( ild) by default instead of the linker ( ld) for link-only invocations of the compiler. That is, with -g, the compiler’s default behavior was to automatically invoke ild in place of ld whenever you used the compiler to link object files, unless you specified -G or source files on the command line. This is no longer the case. The incremental linker is no longer available.
For more information on debugging, see the Debugging a Program With dbx manual.