Re: RFA: Search for symbol names the same way they're hashed.

[Daniel Berlin <dberlin at dberlin dot org>]

On Wednesday, October 2, 2002, at 03:18  PM, Jim Blandy wrote:

> I just did a quick survey of the uses of SYMBOL_SOURCE_NAME.  They all
> fall into two categories:
> - printing symbol names, and
> - sort comparison functions.
>
> The first usage is exactly correct: the way a symbol prints should
> respect the current demangling setting.
>
> The second usage seems wrong to me: if you sort under one demangling
> setting, but then search under a different one, well, ... duh.
SYMBOL_SOURCE_NAME changes won't help here, it'll only fix half the 
problem.

Try setting a demangling style that is wrong (say EDG), then loading a 
C++ file (ie reading it's symbols), then setting the right demangling 
style.

Observe:
[dberlin@dberlin gdb]$ ./gdb
GNU gdb 2002-08-15-cvs
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and 
you are
welcome to change it and/or distribute copies of it under certain 
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for 
details.
This GDB was configured as "i686-pc-linux-gnu".
Setting up the environment for debugging gdb.
.gdbinit:5: Error in sourced command file:
No symbol table is loaded.  Use the "file" command.
(gdb) set demangle-style edg
(gdb) file a.out
Reading symbols from a.out...done.
(gdb) info func bob
All functions matching regular expression "bob":

File testcpp.cpp:
int _Z3bobv(void);
(gdb) set demangle-style gnu
gnu     gnu-v3
(gdb) set demangle-style gnu-v3
(gdb) info func bob
All functions matching regular expression "bob":

File testcpp.cpp:
int _Z3bobv(void);
(gdb) b bob
Function "bob" not defined.
(gdb)

Even after you set the right demangling style, it's too late.
The symbols in the symbol table will have the wrong demangled names, so 
even if you made SYMBOL_DEMANGLEST or whatever, it will still be wrong.

We need to make demangling-style only affect *printout* and *user 
entered strings*, and during symbol reading, force it to auto, so it 
always gets the right names in the symbol table in the first place.


> The source code name of a symbol does not depend depend on the current
> demangling setting;
And to enforce this, you have to make the readers *not* honor the 
demangling style. If you just fix SYMBOL_SOURCE_NAME, 
SYMBOL_INIT_DEMANGLED_NAME will still be only called once, and it'll 
have the wrong demangling style when it calls cplus_demangle, resulting 
in the symbol having the wrong demangled name forevermore.