projects / binutils.git / blame
| Commit | Line | Data |
|---|---|---|
| 0e39a8bb RP |
1 | |
| 2 | The GAS Configuration Plan | |
| 3 | ||
| 4 | Theory: | |
| 5 | ||
| 6 | The goal of the new configuration scheme is to bury all object format, | |
| 7 | target processor, and host machine dependancies in object, target, and | |
| 8 | host specific files. That is, to move all #ifdef's out of the gas | |
| 9 | common code. | |
| 10 | ||
| 11 | Here's how it works. There is a .h and a .c file for each object file | |
| 12 | format, a .h and a .c file for each target processor, and a .h for | |
| 13 | each host. config.gas creates {sym}links in the current directory to | |
| 14 | the appropriate files in the config directory. config.gas also serves | |
| 15 | as a list of triplets {host, target, object-format} that have been | |
| 16 | tested at one time or another. I also recommend that config.gas be | |
| 17 | used to document triplet specific notes as to purpose of the triplet, | |
| 18 | etc. | |
| 19 | ||
| 20 | Implementation: | |
| 21 | ||
| 22 | host.h is a {sym}link to .../config/xm-yourhost.h. It is intended to | |
| 23 | be used to hide host compiler, system header file, and system library | |
| 24 | differences between host machines. If your host needs actual c source | |
| 25 | files, then either: these are generally useful functions, in which | |
| 26 | case you should probably build a local library outside of the gas | |
| 27 | source tree, or someone, perhaps me, is confused about what is needed | |
| 28 | by different hosts. | |
| 29 | ||
| 30 | obj-format.h is a {sym}link to .../config/obj-something.h. It is intended | |
| 31 | ||
| 32 | All gas .c files include as.h. | |
| 33 | ||
| 34 | as.h #define's "gas", includes host.h, defines a number of gas | |
| 35 | specific structures and types, and then includes tp.h, obj.h, and | |
| 36 | target-environment.h. | |
| 37 | ||
| 38 | target-environment.h defines a target environment specific | |
| 39 | preprocessor flag, eg, TE_SUN, and then includes obj-format.h. | |
| 40 | ||
| 41 | obj-format.h defines an object format specific preprocessor flag, eg, | |
| 42 | OBJ_AOUT, OBJ_BOUT, OBJ_COFF, includes "target-processor.h", and then | |
| 43 | defines the object specific macros, functions, types, and structures. | |
| 44 | ||
| 45 | target-processor.h | |
| 46 | ||
| 47 | target-processor. | |
| 48 | ||
| 49 | Porting: | |
| 50 | ||
| 51 | There appear to be four major types of ports; new hosts, new target | |
| 52 | processors, new object file formats, and new target environments. |