Messages in this thread | | | From | Sergei Trofimovich <> | Subject | [PATCH 0/7] uselex.rb as a tiny tool to find dead code | Date | Thu, 8 Aug 2013 00:43:16 +0300 |
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From: Sergei Trofimovich <slyfox@gentoo.org>
Hi guys!
TL;DR:
the patches remove (currently or already) dead code and localize symbol visibility used only in one module.
Thanks!
The Story:
Once upon a time I've got very simple idea to find dead code in large C/C++ mixed project at work.
The things of my primary interest were things of too large visibility scope, like: - externally visible global variables used only in module defining the variable - and functions of the same property
Once you identify those functions and mark as 'static' you achieve two goals:
- minor: give compiler possibility to inline code a bit better (especially for one-caller case) - more interesting: possibility to spot that the symbol is no longer used at all
Hence the project idea: 1. scan all intermediate object (.o) files for exported symbols 2. find such symbols that are not imported into any .o files
Meet uselex.rb: one-file script to parse 'nm' output:
https://github.com/trofi/uselex/blob/master/uselex.rb
For linux's kernel it's use is as simple as:
$ make $config && make $ uselex.rb `find -name '*.o'`
and you've got material to look at!
It outputs 3000 symbols thus I've started small:
$ uselex.rb `find fs/btrfs -name '*.o'
To get an impression it reports such things:
set_state_private: [R]: exported from: fs/btrfs/built-in.o fs/btrfs/btrfs.o fs/btrfs/extent_io.o btrfs_get_inode_ref_index: [R]: exported from: fs/btrfs/built-in.o fs/btrfs/inode-item.o fs/btrfs/btrfs.o btrfs_print_tree: [R]: exported from: fs/btrfs/built-in.o fs/btrfs/print-tree.o fs/btrfs/btrfs.o btrfs_reada_detach: [R]: exported from: fs/btrfs/built-in.o fs/btrfs/reada.o fs/btrfs/btrfs.o __btrfs_getxattr: [R]: exported from: fs/btrfs/built-in.o fs/btrfs/xattr.o fs/btrfs/btrfs.o __btrfs_setxattr: [R]: exported from: fs/btrfs/built-in.o fs/btrfs/xattr.o fs/btrfs/btrfs.o btrfs_read_root_item: [R]: exported from: fs/btrfs/root-tree.o fs/btrfs/built-in.o fs/btrfs/btrfs.o __tracepoint_btrfs_sync_fs: [R]: exported from: fs/btrfs/super.o fs/btrfs/built-in.o fs/btrfs/btrfs.o btrfs_start_transaction_lflush: [R]: exported from: fs/btrfs/transaction.o fs/btrfs/built-in.o fs/btrfs/btrfs.o btrfs_write_and_wait_marked_extents: [R]: exported from: fs/btrfs/transaction.o fs/btrfs/built-in.o fs/btrfs/btrfs.o ulist_fini: [R]: exported from: fs/btrfs/ulist.o fs/btrfs/built-in.o fs/btrfs/btrfs.o ulist_init: [R]: exported from: fs/btrfs/ulist.o fs/btrfs/built-in.o fs/btrfs/btrfs.o
You just need to make sure it does not lie too much.
For example '__btrfs_getxattr' needs to be brought under '#ifdef CONFIG_BTRFS_FS_POSIX_ACL' and not removed entirely.
Thanks for your patience!
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