Compiling with AddressSanitizer using gcc ≥4.9 breaks printng some variables in gdb on Linux about address-sanitizer

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Note that GCC sometimes optimizes variables in frontend regardless of 
optimization level.

Original comment by [email protected] on 22 May 2015 at 6:35

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But why '-fsanitize=address' changes optimizations?

It's possible that it's something with gcc internals, but ever since I'm 
working on pretty big C89 project compiled on gcc-s 2.95.3-5.1 I've *never* 
encountered '<optimized out>' without '-O' switch, especially with a '-g' one…

That variable should not be optimized out since it's passed around and written 
into. Any combination of '-O' and  '-g' switches  doesn't stop it from 
„disappearing”, also making the variable volatile (!). Only disabling ASAN.

Original comment by [email protected] on 22 May 2015 at 7:07

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Ah, sorry, I thought you meant t. I've check compiler dumps with 
-fdump-tree-all and it looks like d is preserved by ASan:

 $ cat test.c.169t.optimized
 ...
 ;; Function main (main, funcdef_no=3, decl_uid=2584, symbol_order=3)

 main ()
 {
   <bb 2>:
   d = 4;
   t = "";
   fun_wr (&d);

Perhaps GCC has some problem when generating debuginfo? Could you file a bug in 
GCC bugzilla?

Original comment by [email protected] on 22 May 2015 at 7:49

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Already did. Year ago :-(

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61071

I don't think it's a problem with debuginfo, since decreasing size of t by one 
makes printing the d variable work again.

Original comment by [email protected] on 22 May 2015 at 8:01

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Does this work with fresh clang? 
I afraid that this is gcc-specific and there is little we can do on asan side. 

Original comment by [email protected] on 22 May 2015 at 5:44

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> Does this work with fresh clang? 
Yeah, clang produces debugable binary.
clang version 3.6.0 (tags/RELEASE_360/final)

> I afraid that this is gcc-specific and there is little we can do on asan 
side. 
I understand. Thanks for your time, though.

Original comment by [email protected] on 25 May 2015 at 5:18

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Adding Project:AddressSanitizer as part of GitHub migration.

Original comment by [email protected] on 30 Jul 2015 at 9:06

• Added labels: ProjectAddressSanitizer