Chapter 24. Compiler and Linker Options

eCos is built using the GNU C and C++ compilers. eCos relies on certain features of these tools such as constructor priority ordering and selective linking which are not part of other toolchains.

Some GCC options are required for eCos, and others can be useful. This chapter gives a brief description of the required options as well as some recommended eCos-specific options. All other GCC options (described in the GCC manuals) are available.

Compiling a C Application

The following command lines demonstrate the minimum set of options required to compile and link an eCos program written in C.

Note: Remember that when this manual shows TARGET-gcc you should use the full name of the cross compiler, e.g. i386-elf-gcc, arm-eabi-gcc, or sh-elf-gcc. When compiling for the synthetic Linux target, use the native gcc which must have the features required by eCos.

$ TARGET-gcc -c  -IINSTALL_DIR/include file.c
$ TARGET-gcc -o program file.o -LINSTALL_DIR/lib -Ttarget.ld -nostdlib

Note: Certain targets may require extra options, for example the SPARClite architectures require the option -mcpu=sparclite. Examine the BASE_DIR/examples/Makefile or the “Global compiler flags” option (CYGBLD_GLOBAL_CFLAGS) in your generated eCos configuration) to see if any extra options are required, and if so, what they are.

The following command lines use some other options which are recommended because they use the selective linking feature:

$ TARGET-gcc -c  -IINSTALL_DIR/include -I. -ffunction-sections -fdata-sections -g -O2 file.c
$ TARGET-gcc -o program file.o -ffunction-sections -fdata-sections -Wl,--gc-sections -g -O2 \
          -LINSTALL_DIR/lib -Ttarget.ld -nostdlib
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