From: Bo Yang Date: Fri, 23 Apr 2010 03:55:44 GMT Subject: Re: [PATCH 1/2 v3] Make diffcore_std only can run once before a diff_flush. Message-ID: In-Reply-To: <7v1ve743vb.fsf@alter.siamese.dyndns.org> On Fri, Apr 23, 2010 at 4:41 AM, Junio C Hamano wrote: > It actually is stronger than that; we should never run it more than once, > and it would be a bug if we did so.  Which codepath tries to call *_std() > twice? In command 'git log --follow ...' log_tree_diff call diff_tree_sha1 and then diff_tree_diff_flush, when '--follow' is given, the former function will call try_to_follow_renames, which will call diffcore_std to detect rename. And then, diff_tree_diff_flush call 'diffcore_std' again unconditional. (and I have try to find a condition to make the call, but I fail, so I figure out this patch.) Breakpoint 1, diffcore_std (options=0xbf9cc044) at diff.c:3748 3748 if (diff_queued_diff.run) (gdb) bt #0 diffcore_std (options=0xbf9cc044) at diff.c:3748 #1 0x08124206 in try_to_follow_renames (t1=0xbf9cc130, t2=0xbf9cc11c, base=0x81571c9 "", opt=0xbf9cc468) at tree-diff.c:358 #2 0x08124480 in diff_tree_sha1 (old=0x9c51d8c "$\033\222T���\a\035\200T����\210;8\235i", new=0x9c51d2c "\201�\017<�\v��n]\226{�+�\001\003\232\232\230", base=0x81571c9 "", opt=0xbf9cc468) at tree-diff.c:418 #3 0x080e660e in log_tree_diff (opt=0xbf9cc220, commit=0x9c51d28, log=0xbf9cc1ac) at log-tree.c:536 #4 0x080e668f in log_tree_commit (opt=0xbf9cc220, commit=0x9c51d28) at log-tree.c:560 #5 0x0807faa1 in cmd_log_walk (rev=0xbf9cc220) at builtin/log.c:237 #6 0x080806e2 in cmd_log (argc=5, argv=0xbf9cc788, prefix=0x0) at builtin/log.c:481 #7 0x0804b8eb in run_builtin (p=0x8161524, argc=5, argv=0xbf9cc788) at git.c:260 #8 0x0804ba51 in handle_internal_command (argc=5, argv=0xbf9cc788) at git.c:416 #9 0x0804bb2c in run_argv (argcp=0xbf9cc700, argv=0xbf9cc704) at git.c:458 #10 0x0804bcbe in main (argc=5, argv=0xbf9cc788) at git.c:529 (gdb) c Continuing. Breakpoint 1, diffcore_std (options=0xbf9cc468) at diff.c:3748 3748 if (diff_queued_diff.run) (gdb) bt #0 diffcore_std (options=0xbf9cc468) at diff.c:3748 #1 0x080e6356 in log_tree_diff_flush (opt=0xbf9cc220) at log-tree.c:449 #2 0x080e6619 in log_tree_diff (opt=0xbf9cc220, commit=0x9c51d28, log=0xbf9cc1ac) at log-tree.c:537 #3 0x080e668f in log_tree_commit (opt=0xbf9cc220, commit=0x9c51d28) at log-tree.c:560 #4 0x0807faa1 in cmd_log_walk (rev=0xbf9cc220) at builtin/log.c:237 #5 0x080806e2 in cmd_log (argc=5, argv=0xbf9cc788, prefix=0x0) at builtin/log.c:481 #6 0x0804b8eb in run_builtin (p=0x8161524, argc=5, argv=0xbf9cc788) at git.c:260 #7 0x0804ba51 in handle_internal_command (argc=5, argv=0xbf9cc788) at git.c:416 #8 0x0804bb2c in run_argv (argcp=0xbf9cc700, argv=0xbf9cc704) at git.c:458 #9 0x0804bcbe in main (argc=5, argv=0xbf9cc788) at git.c:529 (gdb) > The standard calling sequence is: > >  - start from an empty queue. > >  - use diff_change() and diff_addremove() to populate the queue. > >  - call diffcore_std(). if you need to use a non-standard chain of >   diffcore transformations, you _could_ call the diffcore_* routines that >   diffcore_std() calls, if you choose to, but as you found out, some of >   them are not idempotent operations, and shouldn't be called twice. > >  - and finally call diffcore_flush(). > >> @@ -3745,6 +3742,12 @@ void diffcore_fix_diff_index(struct diff_options *options) >> >>  void diffcore_std(struct diff_options *options) >>  { >> +     /* We never run this function more than one time, because the >> +      * rename/copy detection logic can only run once. >> +      */ >> +     if (diff_queued_diff.run) >> +             return; > > Shouldn't this be a BUG() instead? Anyone may call diff_tree_sha1 and then diffcore_std, and diff_tree_sha1 may call another diffcore_std if '--follow' given. If this is a BUG, the calling pattern, diff_tree_sha1 -> diffcore_std should all disappear from our code. And this involved much code refactor. And I suggest my way that we avoid the duplicate call actively in diffcore_std. > The trivial rewrite to use this macro is a good idea, but it probably > should be a separate patch. > >> +#define DIFF_QUEUE_CLEAR(q) \ >> +     do { \ >> +             (q)->queue = NULL; \ >> +             (q)->nr = (q)->alloc = (q)->run = 0; \ >> +     } while(0); > You mean split this commit into two? Regards! Bo -- My blog: http://blog.morebits.org