17.2.2 Address Function Attribute

The address(addr) attribute specifies an absolute physical address at which the attributed routine will be placed in memory. It can be used with C and C++ functions.

__attribute__((address(0x460000))) void bar (void);

The compiler performs no error checking on the address. The section containing the function will be located at the specified address regardless of the memory-regions specified in the linker script or the actual memory ranges on the target device. The application code must ensure that the address is valid for the target device.

Sections used to hold functions placed at an absolute address will use a name .address.N.decl, where N is the address and decl is the name of the declaration.

To make effective use of absolute sections and the new best-fit allocator, standard program-memory and data-memory sections should not be mapped in the linker script. The built-in linker script does not map most standard sections such as the .text, .data, .bss, or .ramfunc sections. By not mapping these sections in the linker script, we allow these sections to be allocated using the best-fit allocator rather than the sequential allocator. Sections that are unmapped in the linker script can flow around absolute sections, whereas sections that are linker-script mapped are grouped together and allocated sequentially, potentially causing conflicts with absolute sections.