Difference between revisions of "Compiler development articles"
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Jump to navigationJump to search (Found a nice link about C++ objects in Delphi, Hope that remark about negative VMT offsets is correct) |
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Note that FPC doesn't have negative VMT offsets due to GNU LD limitations. | Note that FPC doesn't have negative VMT offsets due to GNU LD limitations. | ||
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+ | The fundament of above C++ <-> OPas lies in COM interfaces: (quote from Rudy Velthuis) | ||
+ | |||
+ | "Well, all compilers must be able to create COM interfaces. Since in | ||
+ | C++, these are simply pure abstract classes, and Delphi must have the | ||
+ | same layout, for many reasons, they are all compatible. In fact, a pure | ||
+ | abstract class pointer points to a structure of which the first entry | ||
+ | is a VMT. This is also how interfaces are built" | ||
= Processor dependent = | = Processor dependent = |
Revision as of 10:56, 10 April 2005
The current FPC version under developement is 1.9.x. Compiler internals are documented at the evolving FPC internals page.
General
Enable new style smartlinking (freebsd,linux)
- in i_*.pas add tf_smartlink_sections to the flags field of the platform description record for your OS/CPU combo (in my case i_bsd.pas, the system_i386_freebsd_info record)
- in ogelf.pas scroll down to nearly the bottom, and add af_smartlink_sections to the flags field of as_i386_elf32_info
- run "(g)make all OPT='-Aas -k--gc-sections' at the toplevel to build using new smartlinking routines.
C++ linking
See http://rvelthuis.bei.t-online.de/articles/articles-cppobjs.htm
Note that FPC doesn't have negative VMT offsets due to GNU LD limitations.
The fundament of above C++ <-> OPas lies in COM interfaces: (quote from Rudy Velthuis)
"Well, all compilers must be able to create COM interfaces. Since in C++, these are simply pure abstract classes, and Delphi must have the same layout, for many reasons, they are all compatible. In fact, a pure abstract class pointer points to a structure of which the first entry is a VMT. This is also how interfaces are built"