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From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug gdb/25528] step will stopped at any "asm volatile" statement
Date: Wed, 30 Dec 2020 17:16:13 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D25528

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|FIXED                       |NOTABUG

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Yibiao Yang from comment #0)
> $ gdb -q ./a.out
> Reading symbols from ./a.out...
> (gdb) break small.c:9
> Breakpoint 1 at 0x113f: file small.c, line 9.
> (gdb) run
> Starting program: /home/yibiao/cv-gcov/a.out=20
>=20
> Breakpoint 1, f (delta=3D-1) at small.c:9
> 9	    if (NM[p] =3D=3D 0)
> (gdb) step
> 10	      asm volatile("");
> (gdb) c
> Continuing.
>=20
> Breakpoint 1, f (delta=3D-1) at small.c:9
> 9	    if (NM[p] =3D=3D 0)
> (gdb) step
> 10	      asm volatile("");
> (gdb) q
> A debugging session is active.
>=20
> 	Inferior 1 [process 4947] will be killed.
>=20
> Quit anyway? (y or n) y
>=20
>=20
>=20
> #########################################################################=
####
> ##
> ### We can find that Line #10 @asm volatile("");@ is executed twice.=20
> ### However, it is obvious that Line #9 "if (NM[p] =3D=3D 0)" is True in =
the
> second for loop.=20
> #########################################################################=
####
> ##

I think this is a different variant of the same problem: the target of the =
true
_and_ false path end up at the same insn, which has two entries in the line
table.  So either we show the "true" line twice, or the "false" line twice.

Confusing, but not a gdb bug.

On the gcc side, it could be argued that this is exactly what you asked for=
 by
providing an _empty_ asm stmt.

--=20
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