Re: [PATCH v4 2/2] gdb: CTF support

[Wei-min Pan <weimin.pan@oracle.com>]

On 10/7/2019 7:40 AM, Simon Marchi wrote:
> On 2019-10-04 4:23 p.m., Weimin Pan wrote:
>> This patch adds the CTF (Compact Ansi-C Type Format) support in gdb.
>> Two submissions on which this gdb work depends were posted earlier
>> in May:
>>
>>   * On the binutils mailing list - adding libctf which creates, updates,
>>     reads, and manipulates the CTF data.
>>   * On the gcc mailing list - expanding gcc to directly emit the CFT data
>>     with a new command line option -gt.
>>
>> CTF is a reduced form of debugging information whose main purpose is to
>> describe the type of C entities such as structures, unions, typedefs and
>> function arguments at the global scope only. It does not contain debug
>> information about source lines, location expressions, or local variables.
>> For more information on CTF, see the documentation in the libdtrace-ctf
>> source tree, available here:
>>
>> <https://raw.githubusercontent.com/oracle/libdtrace-ctf/master/doc/ctf-format>.
>>
>> This patch expands struct elfinfo by adding the .ctf section, which
>> contains CTF debugging info, and modifies elf_symfile_read() to read it.
>> If both DWARF and CTF exist in a program, only DWARF will be read. CTF data
>> will be read only when there is no DWARF. The two-stage symbolic reading
>> and setting strategy, partial and full, was used.
>>
>> File ctfread.c contains functions to transform CTF data into gdb's internal
>> symbol table structures by iterately reading entries from CTF sections
>> of "data objects", "function info", "variable info", and "data types"
>> when setting up either partial or full symbol table. If the ELF symbol table
>> is available, e.g. not stripped, the CTF reader will associate the found
>> type information with these symbol entries. Due to the proximity between DWARF
>> and CTF (CTF being a much simplified subset of DWARF), some DWARF implementation
>> was reused to support CTF.
>>
>> Test cases ctf-constvars.exp, ctf-cvexpr.exp, ctf-ptype.exp, and ctf-whatis.exp
>> have been added to verify the correctness of this support.
>>
>> This patch has missing features and limitations which we will add and
>> address in the future patches.
> Hi Weimin,
>
> I got notified this morning that this patch series was pushed to master, although it
> was not approved yet.  I don't think I had any remaining comments and was probably going
> to approve this version anyway, but I am wondering if you pushed this version to master
> by mistake instead of your personal users/ branch, since I told you to do so.

Hi Simon,

I'm very sorry, should've pushed it to my private branch, my fault.

Weimin
>
> Please just fix up the ChangeLog entry below:
>
>> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
>> index 3974823..03b9474 100644
>> --- a/gdb/ChangeLog
>> +++ b/gdb/ChangeLog
>> @@ -1,5 +1,20 @@
>>   2019-10-04  Weimin Pan  <weimin.pan@oracle.com>
>>   
>> +	* ctfread.c: New file.
>> +	* ctfread.h: New file.
>> +	* elfread.c: Include ctfread.h.
>> +	(struct elfinfo text_p): New member ctfsect.
>> +	(elf_locate_sections): Mark CTF section.
>> +	(elf_symfile_read): Call elfctf_build_psymtabs.
>> +	* Makefile.in (LIBCTF): Add.
>> +	(CLIBS): Use it.
>> +	(CDEPS): Likewise.
>> +	(DIST): Add ctfread.c.
>> +	* ../Makefile.def (dependencies): Add all-libctf to all-gdb
>> +	* ../Makefile.in: Add "all-gdb: maybe-all-libctf"
> As mentioned in the previous review, these last two lines must go in the top-level ChangeLog.
>
> Simon