Determines whether EBP is used as a general-purpose register in optimizations.
Windows: Optimization > Omit Frame Pointers
Linux: None
Mac OS X: Optimization > Provide Frame Pointer
-f[no-]omit-frame-pointer: IA-32 architecture, Intel® 64 architecture
/Oy[-]: IA-32 architecture
Linux and Mac OS X: | -fomit-frame-pointer -fno-omit-frame-pointer |
Windows: | /Oy /Oy- |
None
-fomit-frame-pointer |
EBP is used as a general-purpose register in optimizations. However, on Linux* and Mac OS X systems, the default is -fno-omit-frame-pointer if option -O0 or -g is specified. On Windows* systems, the default is /Oy- if option /Od is specified. |
These options determine whether EBP is used as a general-purpose register in optimizations. Options -fomit-frame-pointer and /Oy allow this use. Options -fno-omit-frame-pointer and /Oy- disallow it.
Some debuggers expect EBP to be used as a stack frame pointer, and cannot produce a stack backtrace unless this is so. The -fno-omit-frame-pointer and /Oy- options direct the compiler to generate code that maintains and uses EBP as a stack frame pointer for all functions so that a debugger can still produce a stack backtrace without doing the following:
For -fno-omit-frame-pointer: turning off optimizations with -O0
For /Oy-: turning off /O1, /O2, or /O3 optimizations
The -fno-omit-frame-pointer option is set when you specify option -O0 or the -g option. The -fomit-frame-pointer option is set when you specify option -O1, -O2, or -O3.
The /Oy option is set when you specify the /O1, /O2, or /O3 option. Option /Oy- is set when you specify the /Od option.
Using the -fno-omit-frame-pointer or /Oy- option reduces the number of available general-purpose registers by 1, and can result in slightly less efficient code.