9.5.6 Other Linker Script Commands

Assert Command

The ASSERT(exp, message) command ensures that exp is non-zero. If it is zero, then exit the linker with an error code, and print message.

Entry Command

The ENTRY(symbol) command specifies symbol as the first instruction to execute in the program. The linker will record the address of this symbol in the output object file header. This does not affect the Reset instruction at address zero, which must be generated in some other way. By convention, the 32-bit linker scripts construct a GOTO _ _reset instruction at address zero.

Extern Command

The EXTERN(symbol symbol ...) command forces symbol to be entered in the output file as an undefined symbol. Doing this may, for example, trigger linking of additional modules from standard libraries. Several symbols may be listed for each EXTERN, and EXTERN may appear multiple times. This command has the same effect as the -u command line option.

Force_common_allocation Command

The FORCE_COMMON_ALLOCATION command has the same effect as the -d command line option: to make 32-bit linker assign space to common symbols even if a relocatable output file is specified (-r).

Nocrossrefs Command

The NOCROSSREFS(section section ...) command may be used to tell 32-bit linker to issue an error about any references among certain output sections. In certain types of programs, when one section is loaded into memory, another section will not be. Any direct references between the two sections would be errors.

The NOCROSSREFS command takes a list of output section names. If the linker detects any cross references between the sections, it reports an error and returns a non-zero exit status. The NOCROSSREFS command uses output section names, not input section names.

Output_arch Command

The OUTPUT_ARCH(bfdarch) command specifies a particular output machine architecture. The bfdarch value is pic32mx for Microchip PIC32 MCUs, for example. Other values for ARm-based devices include armv5tej, armv6s-m, armv7, armv7e-m, armv8-m.base and armv8-m.main.

Output_format Command

The OUTPUT_FORMAT(format_name) command names the object file format to use for the output file. The format_name value is always elf32-tradlittlemips for Microchip PIC32 MCUs.

Target Command

The TARGET(format_name) command names the object file format to use when reading input files. It affects subsequent INPUT and GROUP commands. The format_name value should remain elf32-tradlittlemips for Microchip PIC32 MCUs.