05/07/2022 09:39, Sven Barth via fpc-devel wrote:
Joost van der Sluis via fpc-devel <fpc-devel@lists.freepascal.org
<mailto:fpc-devel@lists.freepascal.org>> schrieb am Di., 5. Juli 2022, 00:17:
But my real issue is this: on Windows, using the internal linker, this
procedure is also omitted *with* Dwarf debug-data. As you implied.
The problem is, though, that the CFI-information (the FDE) is not
omitted. This is 'solved' in the internal linker by replacing the
address with 0. Gdb doesn't mind and I've adapted FpDebug so that it
allows this too, but this is still invalid, imho.
But as the FDE is written now, as 'one block', without any sections, I
don't see how the linker could omit the corresponding FDE.
Any suggestions? Is it possible to place every fde in it's own section
to solve this?
The problem is that *something* would need to reference the debug sections otherwise they are
stripped as well. But as soon as they're referenced whatever code or data *they* reference is kept
as well.
One of the better solutions might be to write these references as weak symbols (on systems that
support this) so at least the data/function isn't kept around.
Or the section of the data/function would have to contain a reference to its corresponding debug
entry so that it is kept around as long as the function/data is kept around...
How does GCC do this?
As far as I had studied this issue, ld essentially "decompiles" the monolithic FDE's from object
files into internal representation, and then "compiles" it back, omitting information for the code
that won't go into executable due to smartlinking. It also optimizes for size by using 8- and 16-bit
offsets instead of 32-bit ones when possible.
Regards,
Sergei
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