> On 15-Jul-2021, at 4:53 AM, David Malcolm <dmalc...@redhat.com> wrote:
>
> On Wed, 2021-07-14 at 22:41 +0530, Ankur Saini wrote:
>> CURRENT STATUS OF PROJECT:
>>
>> - The analyzer can now sucessfully detect and analyze function calls
>> that
>> doesn't have a callgraph edge ( like a call via function pointer )
>
> Excellent.
>
>>
>> - A weird indentation problem caused by my text editor pointed out in
>> one of the previous mails (
>> https://gcc.gnu.org/pipermail/gcc/2021-July/236747.html)
>> , that despite being fixed, still messed up indentation in all of
>> the changes
>> I have done so far.
>>
>> - the analyser can still not detect a call via vtable pointer
>>
>> ---
>> AIM FOR TODAY:
>>
>> - Complete the first evaluation of GSoC
>> - Fix the indentation errors my generated by my editor on changes
>> done till now
>> - Add the tests to regress testing
>> - Create a ChangeLog for the next patch
>> - Attach the patch with this mail
>> - Layout a new region subclass for vtables ( getting ready for next
>> patch )
>>
>> ---
>> PROGRESS :
>>
>> - To fix the indentaion problem, I simply created a diff and fixed
>> all of them
>> manually. I also found and read a doc regarding coding convention
>> used by GCC
>> (https://gcc.gnu.org/codingconventions.html) and refactored the
>> chagnes and
>> changelog to follow this.
>
> Great.
>
>>
>> - After that I branched out and layed out foundation for next update
>> and started created a subclass region for vtable ( vtable_region ),
>> which
>> currently do nothing
>>
>> - After that in order to give some final finishing touches to
>> previous changes,
>> I created chagnelog and added 2 more tests to the analyzer
>> testsuite as
>> follows :
>>
>> 1. (function-ptr-4.c)
>> ```
> [...snip...]
>> ```
>> (godbolt link <https://godbolt.org/z/1o3cK4aYo
>> <https://godbolt.org/z/1o3cK4aYo>>)
>
> Looks promising.
>
> Does this work in DejaGnu? The directive:
> /* { dg-warning "double-‘free’ of ‘int_ptr’" } */
> might need changing to:
> /* { dg-warning "double-'free' of 'int_ptr'" } */
> i.e. fixing the quotes to use ASCII ' rather than ‘ and ’.
>
> It's worth running the testcases with LANG=C when generating the
> expected outputs. IIRC this is done automatically by the various "make
> check-*”.
ok
>
>
>>
>> 2. ( pr100546.c <
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100546
>> <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100546>>)
>> ```
>> #include <stdio.h>
>> #include <cstdlib.h>
>>
>> static void noReturn(const char *str) __attribute__((noreturn));
>> static void noReturn(const char *str) {
>> printf("%s\n", str);
>> exit(1);
>> }
>>
>> void (*noReturnPtr)(const char *str) = &noReturn;
>>
>> int main(int argc, char **argv) {
>> char *str = 0;
>> if (!str)
>> noReturnPtr(__FILE__);
>> return printf("%c\n", *str);
>> }
>> ```
>> (godbolt link <https://godbolt.org/z/aWfW51se3
>> <https://godbolt.org/z/aWfW51se3>>)
>>
>> - But at the time of testing ( command used
>> was `make check-gcc RUNTESTFLAGS="-v -v analyzer.exp=pr100546.c"`),
>> both of
>> them failed unexpectedly with Segmentation fault at the call
>>
>> - From further inspection, I found out that this is due
>> "-fanalyzer-call-summaries" option, which looks like activats call
>> summaries
>>
>> - I would look into this in more details ( with gdb ) tomorrow, right
>> now
>> my guess is that this is either due too the changes I did in state-
>> purge.cc <http://purge.cc/>
>> or is a call-summary related problem ( I remember it not being
>> perfetly implemented right now).
>
> I'm not proud of the call summary code, so that may well be the
> problem.
>
> Are you able to use gdb on the analyzer? It ought to be fairly
> painless to identify where a segfault is happening, so let me know if
> you're running into any problems with that.
Yes, I used gdb on the analyzer to go into details and looks like I was
correct, the program was crashing in “analysis_plan::use_summary_p ()” on line
114 ( const cgraph_node *callee = edge->callee; ) where program was trying to
access callgraph edge which didn’t exist .
I fixed it by simply making analyzer abort using call summaries in absence of
callgraph edge.
File: {src-dir}/gcc/analyzer/analysis-plan.cc
105: bool
106: analysis_plan::use_summary_p (const cgraph_edge *edge) const
107: {
108: /* Don't use call summaries if -fno-analyzer-call-summaries. */
109: if (!flag_analyzer_call_summaries)
110: return false;
111:
112: /* Don't use call summaries if there is no callgraph edge */
113: if(!edge || !edge->callee)
114: return false;
and now the tests are passing successfully. ( both manually and via DejaGnu ).
I have attached a sample patch of work done till now with this mail for review
( I haven’t sent this one to the patches list as it’s change log was not
complete for now ).
P.S. I have also sent another mail (
https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575396.html
<https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575396.html> ) to patches
list with the previous call-string patch and this time it popped up in my inbox
as it should, did you also received it now ?
Thanks
- Ankur
