Re: setting a breakpoint on a dll, relative path or absolute path issue

[asmwarrior <asmwarrior@gmail.com>]

On 2011-6-12 11:58, asmwarrior wrote:
> On 2011-6-12 1:08, Keith Seitz wrote:
>> On 06/11/2011 12:52 AM, asmwarrior wrote:
>>> Can you give me a direction that I can dig into the gdb's source?
>>
>> This is almost certainly PR 12843:
>>
>> http://sourceware.org/bugzilla/show_bug.cgi?id=12843
>>
>> This was caused, I believe, by this patch hunk (for locate_first_half in
>> linespec.c), which I committed for c++/12750 on 2011-05-31:
>>
>> @@ -1160,13 +1207,11 @@ locate_first_half (char **argptr, int
>> *is_quote_enclosed
>> break;
>> }
>> /* Check for the end of the first half of the linespec. End of
>> - line, a tab, a double colon or the last single colon, or a
>> - space. But if enclosed in double quotes we do not break on
>> - enclosed spaces. */
>> + line, a tab, a colon or a space. But if enclosed in double
>> + quotes we do not break on enclosed spaces. */
>> if (!*p
>> || p[0] == '\t'
>> - || ((p[0] == ':')
>> - && ((p[1] == ':') || (strchr (p + 1, ':') == NULL)))
>> + || (p[0] == ':')
>> || ((p[0] == ' ') && !*is_quote_enclosed))
>> break;
>> if (p[0] == '.' && strchr (p, ':') == NULL)
>>
>> I am intending to get to this, but it will probably not be until later
>> this coming week.
>>
>> Keith
>>
> Hi, Keith, thanks for the reply. I have reverted the patch hunk in the
> locate_first_half function and build gdb again, now, I can set
> breakpoint like:
>
>  > break
> "E:/code/cb/test_code/debug_wx_library/debug_wx_libraryMain.cpp:101"
> Breakpoint 1 at 0x401d09: file
> E:\code\cb\test_code\debug_wx_library\debug_wx_libraryMain.cpp, line 101.
>
> So, the PR 12843 can be solved.
> ---------------------------------------------------------------
> But what I have mentioned in my OP is another issue about setting
> breakpoint, that is:
>
> gdb failed on setting a breakpoint on a shared dll(the dll is build with
> the relative paths)
>
> break "E:/code/cb/wx/wxWidgets-2.8.12/src/common/string.cpp:164"
> No source file named E:/code/cb/wx/wxWidgets-2.8.12/src/common/string.cpp.
> Breakpoint 2 ("E:/code/cb/wx/wxWidgets-2.8.12/src/common/string.cpp:164)
> pending.
> ------------------------------------------------------------------
> But the breakpoint can be set by using two ways below:
>  > break ../../src/common/string.cpp:164
> Breakpoint 3 at 0x66d89f44: file ../../src/common/string.cpp, line 164.
>  >>>>>>cb_gdb:
>  > break
> E:\code\cb\wx\wxWidgets-2.8.12\build\msw/../../src/common/string.cpp:164
> Breakpoint 4 at 0x66d89f44: file ../../src/common/string.cpp, line 164.
> -------------------------------------------------------------------
> What I expect is the let the first way work.
>
> So, I would like to find some gdb source snippet which handle the file
> path match algorithm, so that all the three methods can work. Can you
> give me a direction?
>
> thanks.
> asmwarrior
> ollydbg from code::blocks' forum
>
>
>
Hi, all, by reading the gdb's source, I found that why setting 
breakpoint faild on this situation, here is my observation:

When I run the gdb command: info sources

Then, I found that there's on source line named:

E:\code\cb\wx\wxWidgets-2.8.12\build\msw/../../src/common/datetime.cpp

This line can be list in symbols or psymbols.

Now, a user try to set a breakpoint, he can use a FILE:LINE format, gdb 
try to match the FILE in all the sources.

The match algorithm was mainly in: gdbgit\gdb\gdb\symtab.c
in function: struct symtab * lookup_symtab (const char *name)

There are three match algorithms involved:
1, exact match
If the user supply the string:
"E:\code\cb\wx\wxWidgets-2.8.12\build\msw/../../src/common/datetime.cpp"
Then, it will have a exact match, and the breakpoint can set correctly.

2, tailed match
If the user supply the string:
"../../src/common/datetime.cpp"
It will still match that string in the symbol table, so it works OK.

3, transferred match, this is why things break down

If the user supply a string:
"E:/code/cb/wx/wxWidgets-2.8.12/src/common/datetime.cpp"
Now, gdb try to below:

const char *fp = symtab_to_fullname (s);

if (fp != NULL && FILENAME_CMP (full_path, fp) == 0)
{
     do_cleanups (cleanup);
     return s;
}
Note, the s is every string shown in the "info sources", and full_path 
is the user supplied string, so if the function symtab_to_fullname (s) 
correctly transferred to
"E:/code/cb/wx/wxWidgets-2.8.12/src/common/datetime.cpp"
Then, this will get matched.

So, as a conclusion:
1, either we should store the
"E:/code/cb/wx/wxWidgets-2.8.12/src/common/datetime.cpp"
instead of
"E:\code\cb\wx\wxWidgets-2.8.12\build\msw/../../src/common/datetime.cpp"
in the symbol tables.


2, or we need to fix the way I said before "transferred match", so they 
can still get matched.

Any ideas?

asmwarrior
ollydbg from codeblocks' forum