-qunwind

Category

Optimization and tuning

Purpose

Specifies that the compiler will preserve the default behavior for saves and restores to volatile registers during a procedure call.

Defaults

-qunwind

Usage

If you specify -qnounwind, the compiler rearranges subprograms to minimize saves and restores to volatile registers. This rearrangement may make it impossible for the program or debuggers to walk through or "unwind" subprogram stack frame chains.

While code semantics are preserved, applications such as exception handlers that rely on the default behavior for saves and restores can produce undefined results. When using -qnounwind in conjunction with the -g compiler option, debugging information regarding exception handling when unwinding the program's stack can be inaccurate.