Determining what object files have caused .dll size increase [C++]

Question

I'm working on a large c++ built library that has grown by a significant amount recently. Due to it's size, it is not obvious what has caused this size increase.

Do you have any suggestions of tools (msvc or gcc) that could help determine where the growth has come from.

edit Things i've tried: Dumpbin the final dll, the obj files, creating a map file and ripping through it.

edit again So objdump along with a python script seems to have done what I want.

Answer 1

G'day,

If you have any previous versions of the object file laying around can you run the size command to see which segment has grown?

Couple of questions:

• Are you on a *nix platform or a Windows platform?
• Which compiler are you using?
• Was the compiler recently changed?
• Was the -g flag added recently? (obvious question 1)
• Was the object previously stripped? (obvious question 2)
• Was the object dynamically linked previously? (obvious question 3)

Edit: If the code is under SCM, can you check out a version of the source that gave you the smaller object. Then compare:

1. the size of the source trees by doing a du -sk on the old source tree and then the new source tree without having built anything.
2. the number of files by doing something like find ./tree_top ( -name *.h -o -name *.cpp ) | wc -l
3. the location of an increased number of files by doing a find ./tree_top ( -name *.h -o -name *.cpp ) -print | sort > treelist and then do the same for the new larger tree. Doing a simple sdiff will show any large number of new files.
4. the size of code base, even a simple count of trailing semi-colons will give you a good basic mechanism for comparison between the two.
5. the Makefiles or build env. for the project to see if different options or settings have crept in to the build itself.

HTH

BTW Please post your findings here as I'm sure many people are interested in what you find out.

cheers,

Answer 2

If gcc, objdump. If visual studio, dumpbin.

I'd suggest doing a diff of the output of the tool for the old (small) library, vs. the new (large) library.

Answer 3

On Linux it should be quite easy to see if new files have been added with a recursive diff. They would certainly create an increase in the library size. You can then go an use the size command line tool on Linux to get the sizes of each of the new object files and sum them up. Then compare that sum to your library increase and check how much it differs.

Answer 4

keysersoze's answer (compare the output of objdump or dumpbin) is correct. Another approach is to tell the linker to produce a map file, and compare the map files for the old and new versions of the DLL.

• MSVC: link.exe /MAP
• GCC and binutils: ld -M (or gcc -Wl,-M)