incremental ld ?

incremental ld ?

[Shyjan Mahamud]

hello, are there any plans for an incremental version of ld 
(i don't mean 'ld -r') ? or is there one already ? 
it is a shame to have to wait *12 min* for the linker to build from scratch
when i may have changed just one line of code. 

thanx
- shyjan

Re: incremental ld ?

[mahamud]

thanx for the prompt reply!

    >> Let me guess - it's a large g++ project compiled with debygging
    >> ?  I had something like this last year.  I fixed it by sending

yes, a module for the mozilla browser project. 

    >> in a patch to ld which did better hashing for the debugging
    >> info (which halved the time) and compiling fewer files with

i assume that this patch has been incorporated into the current ld.

    >> debugging turned on (which got the time to somewhere just
    >> beyond painful).

i did'nt think of this before. i have tried it now, it cuts down on the space
a lot - from ~50MB to ~14MB, but it shaved off only ~2 min from the 
12 min link time.

    >> (My next step would have been to split the binary into
    >> different shared objects)

the code is divided into lots of shared objects,
but the problem i am facing is while creating another shared object
from a bunch of objects and other shared objects. 
most of the object files are not modified. if i wanted to create a
final executable, then i would use your suggestion and create
a new shared object from the object files that don't get modified
and use that along with other shared objects and the 
object files that get modified to create the executable. 

i have tried an alternative suggested by the ld man page.
i used 'ld -Ur' to create a relocatable file from all the object files 
that don't get modified. the man page claims that further linking should be
faster with such a relinkable object file. i then create the shared
object i want with this relinkable object file 
along with the modified object files (as
well as other shared objects). Surprisingly things get worse, ~20 min
vs. 12 min. without 'ld -Ur'. am i doing something wrong ?

while on this topic of relinkable objects, i would like to ask why 
i cannot link in shared objects with the 'ld -Ur' option ?
i can only link in these shared objects while creating the final
shared object using a normal ld. is this a limitation of the current
implementation of gnu ld or is it fundamentally not possible (i am not 
a compiler/linker expert). i would think that if it was possible
to link in shared objects with 'ld -Ur' then a lot more symbols could
get resolved upfront, thus avoiding having to resolve 
these symbols while creating the final shared object. 

any comments and help would be appreciated.

thanx
- shyjan