3.2.7.3 Compiler and Toolchain Options

Table 3-3. AVR® GNU C Compiler Options
Option	Description
General options
-mcall-prologues	Use subroutines for functions prologues and epilogues
-mno-interrupts	Change stack pointer without disabling interrupts
-funsigned-char	The default char type is unsigned
-funsigned-bitfield	The default bit field is unsigned
Preprocessor options
-nostdinc	Do not search the system directories
-E	Preprocess only
Symbols options
Symbols in the source can be defined (-D) or undefined (-U). New symbol declarations can be added, modified, or reordered, using the interface buttons below: Add a new symbol. This symbol and all the following icons are reused with the same meaning in other parts of the Microchip Studio interface. Remove the symbol. Edit the symbol. Move the symbol up in the parsing order. Move the symbol down in the parsing order.
Include directories
Contains all the included header and definition directories, can be modified using the same interface as symbols
Optimization options
Optimization level (drop-down menu): -O0, -O1, -O2, -O3, -Os	No optimization, optimize for speed (level 1 - 3), optimize for size
Other optimization flags (manual input form)	Here you should write optimization flags specific to the platform and your requirements
-ffunction-sections	Prepare functions for garbage collection. If a function is never used, its memory will be scrapped.
-fpack-struct	Pack structure members together
-fshort-enums	Allocate only as many bytes as needed by the enumerated types
-mshort-calls	Use rjmp/rcall limited range instructions on the >8K devices
Debug options
Debug level (drop-down menu): none, -g1, -g2, -g3	Specifies the level of tracing and debugging code and headers left or inserted in the source code
Other debug options (form field)	Architecture specific debug options
Warning messages output options
-Wall	All warnings
-Werror	Escalate warnings to errors
-fsyntax-only	Check syntax only
-pedantic	Check conformity to GNU, raise warnings on non-standard programming practice
-pedantic-errors	Same as above, plus escalate warnings to errors
Miscellaneous options
Other flags (form field)	Input other project-specific flags
-v	Verbose
-ansi	Support ANSI programs
-save-temps	Do not delete temporary files
Option	Description

General options

-mcall-prologues

Use subroutines for functions prologues and epilogues

-mno-interrupts

Change stack pointer without disabling interrupts

-funsigned-char

The default char type is unsigned

-funsigned-bitfield

The default bit field is unsigned

Preprocessor options

-nostdinc

Do not search the system directories

-E

Preprocess only

Symbols options

Symbols in the source can be defined (-D) or undefined (-U). New symbol declarations can be added, modified, or reordered, using the interface buttons below:

Add a new symbol. This symbol and all the following icons are reused with the same meaning in other parts of the Microchip Studio interface.
Remove the symbol.
Edit the symbol.
Move the symbol up in the parsing order.
Move the symbol down in the parsing order.