[PATCH] Avoid depending on destructor order

[PATCH] Avoid depending on destructor order

[Thomas Neumann]

In some scenarios (e.g., when mixing gcc and clang code), it can
happen that frames are deregistered after the lookup structure
has already been destroyed. That in itself would be fine, but
it triggers an assert in __deregister_frame_info_bases that
expects to find the frame.

To avoid that, we now remember that the btree as already been
destroyed and disable the assert in that case.

libgcc/ChangeLog:

	* unwind-dw2-fde.c: (release_register_frames) Remember
	when the btree has been destroyed.
	(__deregister_frame_info_bases) Disable the assert when
	shutting down.
---
  libgcc/unwind-dw2-fde.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
index 919abfe0664..d237179f4ea 100644
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -48,6 +48,7 @@ typedef __UINTPTR_TYPE__ uintptr_type;
  #include "unwind-dw2-btree.h"

  static struct btree registered_frames;
+static bool in_shutdown;

  static void
  release_registered_frames (void) __attribute__ ((destructor (110)));
@@ -57,6 +58,7 @@ release_registered_frames (void)
    /* Release the b-tree and all frames. Frame releases that happen 
later are
     * silently ignored */
    btree_destroy (&registered_frames);
+  in_shutdown = true;
  }

  static void
@@ -282,7 +284,7 @@ __deregister_frame_info_bases (const void *begin)
    __gthread_mutex_unlock (&object_mutex);
  #endif

-  gcc_assert (ob);
+  gcc_assert (in_shutdown || ob);
    return (void *) ob;
  }

-- 
2.34.1

Re: [PATCH] Avoid depending on destructor order

[Jason Merrill]

On 9/19/22 12:20, Thomas Neumann wrote:
> In some scenarios (e.g., when mixing gcc and clang code), it can
> happen that frames are deregistered after the lookup structure
> has already been destroyed. That in itself would be fine, but
> it triggers an assert in __deregister_frame_info_bases that
> expects to find the frame.
> 
> To avoid that, we now remember that the btree as already been
> destroyed and disable the assert in that case.

OK.

> libgcc/ChangeLog:
> 
>      * unwind-dw2-fde.c: (release_register_frames) Remember
>      when the btree has been destroyed.
>      (__deregister_frame_info_bases) Disable the assert when
>      shutting down.
> ---
>   libgcc/unwind-dw2-fde.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
> index 919abfe0664..d237179f4ea 100644
> --- a/libgcc/unwind-dw2-fde.c
> +++ b/libgcc/unwind-dw2-fde.c
> @@ -48,6 +48,7 @@ typedef __UINTPTR_TYPE__ uintptr_type;
>   #include "unwind-dw2-btree.h"
> 
>   static struct btree registered_frames;
> +static bool in_shutdown;
> 
>   static void
>   release_registered_frames (void) __attribute__ ((destructor (110)));
> @@ -57,6 +58,7 @@ release_registered_frames (void)
>     /* Release the b-tree and all frames. Frame releases that happen 
> later are
>      * silently ignored */
>     btree_destroy (&registered_frames);
> +  in_shutdown = true;
>   }
> 
>   static void
> @@ -282,7 +284,7 @@ __deregister_frame_info_bases (const void *begin)
>     __gthread_mutex_unlock (&object_mutex);
>   #endif
> 
> -  gcc_assert (ob);
> +  gcc_assert (in_shutdown || ob);
>     return (void *) ob;
>   }
> 

Re: [PATCH] Avoid depending on destructor order

[Claudiu Zissulescu Ianculescu]

Hi Thomas,

This change prohibits compiling of ARC backend:

> +  gcc_assert (in_shutdown || ob);

in_shutdown is only defined when ATOMIC_FDE_FAST_PATH is defined,
while gcc_assert is outside of any ifdef. Please can you revisit this
line and change it accordingly.

Thanks,
Claudiu

Re: [PATCH] Avoid depending on destructor order

[Thomas Neumann]

Hi Claudiu,

> This change prohibits compiling of ARC backend:
> 
>> +  gcc_assert (in_shutdown || ob);
> 
> in_shutdown is only defined when ATOMIC_FDE_FAST_PATH is defined,
> while gcc_assert is outside of any ifdef. Please can you revisit this
> line and change it accordingly.

I have a patch ready, I am waiting for someone to approve my patch:

https://gcc.gnu.org/pipermail/gcc-patches/2022-September/602130.html

Best

Thomas

Re: [PATCH] Avoid depending on destructor order

[Claudiu Zissulescu Ianculescu]

Thanks, I haven't observed it.

Waiting for it,
Claudiu

On Mon, Sep 26, 2022 at 2:49 PM Thomas Neumann <neumann@in.tum.de> wrote:
>
> Hi Claudiu,
>
> > This change prohibits compiling of ARC backend:
> >
> >> +  gcc_assert (in_shutdown || ob);
> >
> > in_shutdown is only defined when ATOMIC_FDE_FAST_PATH is defined,
> > while gcc_assert is outside of any ifdef. Please can you revisit this
> > line and change it accordingly.
>
> I have a patch ready, I am waiting for someone to approve my patch:
>
> https://gcc.gnu.org/pipermail/gcc-patches/2022-September/602130.html
>
> Best
>
> Thomas

Re: [PATCH] Avoid depending on destructor order

[Iain Sandoe]

> On 26 Sep 2022, at 12:49, Thomas Neumann via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> 
> Hi Claudiu,
> 
>> This change prohibits compiling of ARC backend:
>>> +  gcc_assert (in_shutdown || ob);
>> in_shutdown is only defined when ATOMIC_FDE_FAST_PATH is defined,
>> while gcc_assert is outside of any ifdef. Please can you revisit this
>> line and change it accordingly.
> 
> I have a patch ready, I am waiting for someone to approve my patch:
> 
> https://gcc.gnu.org/pipermail/gcc-patches/2022-September/602130.html

You might also want to include Rainer’s patch,

AFAIR patches to fix bootstrap are allowed to proceed as an exception to
the usual rules,

Iain

Re: [PATCH] Avoid depending on destructor order

[Thomas Neumann]

Hi Iain,

> You might also want to include Rainer’s patch,
> 
> AFAIR patches to fix bootstrap are allowed to proceed as an exception to
> the usual rules,

I was not aware of that. I have pushed the patch below now (including 
Rainer's change), I will update the code if requested.

Best

Thomas

     fix assert in __deregister_frame_info_bases

     When using the atomic fast path deregistering can fail during
     program shutdown if the lookup structures are already destroyed.
     The assert in __deregister_frame_info_bases takes that into
     account. In the non-fast-path case however is not aware of
     program shutdown, which caused a compiler error on such platforms.
     We fix that by introducing a constant for in_shutdown in
     non-fast-path builds.
     We also drop the destructor priority, as it is not supported on
     all platforms and we no longer rely upon the priority anyway.

     libgcc/ChangeLog:
             * unwind-dw2-fde.c: Introduce a constant for in_shutdown
             for the non-fast-path case. Drop destructor priority.

diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
index d237179f4ea..3c0cc654ec0 100644
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -51,7 +51,7 @@ static struct btree registered_frames;
  static bool in_shutdown;

  static void
-release_registered_frames (void) __attribute__ ((destructor (110)));
+release_registered_frames (void) __attribute__ ((destructor));
  static void
  release_registered_frames (void)
  {
@@ -67,6 +67,8 @@ static void
  init_object (struct object *ob);

  #else
+/* Without fast path frame deregistration must always succeed.  */
+static const int in_shutdown = 0;

  /* The unseen_objects list contains objects that have been registered
     but not yet categorized in any way.  The seen_objects list has had

Re: [PATCH] Avoid depending on destructor order

[David Edelsohn]

[-- Attachment #1: Type: text/plain, Size: 380 bytes --]

This patch broke bootstrap on AIX and probably other targets.

#ifdef ATOMIC_FDE_FAST_PATH
#include "unwind-dw2-btree.h"

static struct btree registered_frames;
static bool in_shutdown;
...
#else

in_shutdown only is defined for ATOMIC_FDE_FAST_PATH but used in code /
asserts not protected by that macro.

  gcc_assert (in_shutdown || ob);
  return (void *) ob;
}

Thanks, David

Re: [PATCH] Avoid depending on destructor order

[Thomas Neumann]

> This patch broke bootstrap on AIX and probably other targets.
> 
> #ifdef ATOMIC_FDE_FAST_PATH
> #include "unwind-dw2-btree.h"
> 
> static struct btree registered_frames;
> static bool in_shutdown;
> ...
> #else
> 
> in_shutdown only is defined for ATOMIC_FDE_FAST_PATH but used in code / 
> asserts not protected by that macro.
> 
>    gcc_assert (in_shutdown || ob);
>    return (void *) ob;
> }

I am sorry for that, I did not consider that my test machines all use 
the fast path.

I think the problem can be fixed by the trivial patch below, I will 
commit that after I have tested builds both with and without fast path.

Best

Thomas


diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
index d237179f4ea..d6e347c5481 100644
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -67,6 +67,8 @@ static void
  init_object (struct object *ob);

  #else
+/* Without fast path frame lookup must always succeed */
+static const bool in_shutdown = false;

  /* The unseen_objects list contains objects that have been registered
     but not yet categorized in any way.  The seen_objects list has had

Re: [PATCH] Avoid depending on destructor order

[David Edelsohn]

[-- Attachment #1: Type: text/plain, Size: 1504 bytes --]

On Fri, Sep 23, 2022 at 9:38 AM Thomas Neumann <neumann@in.tum.de> wrote:

> > This patch broke bootstrap on AIX and probably other targets.
> >
> > #ifdef ATOMIC_FDE_FAST_PATH
> > #include "unwind-dw2-btree.h"
> >
> > static struct btree registered_frames;
> > static bool in_shutdown;
> > ...
> > #else
> >
> > in_shutdown only is defined for ATOMIC_FDE_FAST_PATH but used in code /
> > asserts not protected by that macro.
> >
> >    gcc_assert (in_shutdown || ob);
> >    return (void *) ob;
> > }
>
> I am sorry for that, I did not consider that my test machines all use
> the fast path.
>
> I think the problem can be fixed by the trivial patch below, I will
> commit that after I have tested builds both with and without fast path.
>
> Best
>
> Thomas
>
>
> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
> index d237179f4ea..d6e347c5481 100644
> --- a/libgcc/unwind-dw2-fde.c
> +++ b/libgcc/unwind-dw2-fde.c
> @@ -67,6 +67,8 @@ static void
>   init_object (struct object *ob);
>
>   #else
> +/* Without fast path frame lookup must always succeed */
>
The comment should end with full stop and two spaces.


> +static const bool in_shutdown = false;
>
I'll let Jason or others decide if this is the right solution.  It seems
that in_shutdown also could be declared outside the #ifdef and initialized
as "false".

Thanks, David


>
>   /* The unseen_objects list contains objects that have been registered
>      but not yet categorized in any way.  The seen_objects list has had
>

Re: [PATCH] Avoid depending on destructor order

[Thomas Neumann]

> 
>     +static const bool in_shutdown = false;
> 
> I'll let Jason or others decide if this is the right solution.  It seems 
> that in_shutdown also could be declared outside the #ifdef and 
> initialized as "false".

sure, either is fine. Moving it outside the #ifdef wastes one byte in 
the executable (while the compiler can eliminate the const), but it does 
not really matter.

I have verified that the patch below fixes builds for both fast-path and 
non-fast-path builds. But if you prefer I will move the in_shutdown 
definition instead.

Best

Thomas

PS: in_shutdown is an int here instead of a bool because non-fast-path 
builds do not include stdbool. Not a good reason, of course, but I 
wanted to keep the patch minimal and it makes no difference in practice.


     When using the atomic fast path deregistering can fail during
     program shutdown if the lookup structures are already destroyed.
     The assert in __deregister_frame_info_bases takes that into
     account. In the non-fast-path case however is not aware of
     program shutdown, which caused a compiler error on such platforms.
     We fix that by introducing a constant for in_shutdown in
     non-fast-path builds.

     libgcc/ChangeLog:
             * unwind-dw2-fde.c: Introduce a constant for in_shutdown
             for the non-fast-path case.

diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
index d237179f4ea..0bcd5061d76 100644
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -67,6 +67,8 @@ static void
  init_object (struct object *ob);

  #else
+/* Without fast path frame deregistration must always succeed.  */
+static const int in_shutdown = 0;

  /* The unseen_objects list contains objects that have been registered
     but not yet categorized in any way.  The seen_objects list has had

Re: [PATCH] Avoid depending on destructor order

[David Edelsohn]

[-- Attachment #1: Type: text/plain, Size: 2084 bytes --]

On Fri, Sep 23, 2022 at 10:12 AM Thomas Neumann <neumann@in.tum.de> wrote:

> >
> >     +static const bool in_shutdown = false;
> >
> > I'll let Jason or others decide if this is the right solution.  It seems
> > that in_shutdown also could be declared outside the #ifdef and
> > initialized as "false".
>
> sure, either is fine. Moving it outside the #ifdef wastes one byte in
> the executable (while the compiler can eliminate the const), but it does
> not really matter.
>
> I have verified that the patch below fixes builds for both fast-path and
> non-fast-path builds. But if you prefer I will move the in_shutdown
> definition instead.
>
> Best
>
> Thomas
>
> PS: in_shutdown is an int here instead of a bool because non-fast-path
> builds do not include stdbool. Not a good reason, of course, but I
> wanted to keep the patch minimal and it makes no difference in practice.
>
>
>      When using the atomic fast path deregistering can fail during
>      program shutdown if the lookup structures are already destroyed.
>      The assert in __deregister_frame_info_bases takes that into
>      account. In the non-fast-path case however is not aware of
>      program shutdown, which caused a compiler error on such platforms.
>      We fix that by introducing a constant for in_shutdown in
>      non-fast-path builds.
>
>      libgcc/ChangeLog:
>              * unwind-dw2-fde.c: Introduce a constant for in_shutdown
>              for the non-fast-path case.
>
> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
> index d237179f4ea..0bcd5061d76 100644
> --- a/libgcc/unwind-dw2-fde.c
> +++ b/libgcc/unwind-dw2-fde.c
> @@ -67,6 +67,8 @@ static void
>   init_object (struct object *ob);
>
>   #else
> +/* Without fast path frame deregistration must always succeed.  */
> +static const int in_shutdown = 0;
>
>   /* The unseen_objects list contains objects that have been registered
>      but not yet categorized in any way.  The seen_objects list has had
>

Thanks for the patch.  I'll let you and Jason decide which style solution
is preferred.

Thanks, David

Re: [PATCH] Avoid depending on destructor order

[Iain Sandoe]

> On 23 Sep 2022, at 15:30, David Edelsohn via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> 
> On Fri, Sep 23, 2022 at 10:12 AM Thomas Neumann <neumann@in.tum.de> wrote:
> 
>>> 
>>>    +static const bool in_shutdown = false;
>>> 
>>> I'll let Jason or others decide if this is the right solution.  It seems
>>> that in_shutdown also could be declared outside the #ifdef and
>>> initialized as "false".
>> 
>> sure, either is fine. Moving it outside the #ifdef wastes one byte in
>> the executable (while the compiler can eliminate the const), but it does
>> not really matter.
>> 
>> I have verified that the patch below fixes builds for both fast-path and
>> non-fast-path builds. But if you prefer I will move the in_shutdown
>> definition instead.
>> 
>> Best
>> 
>> Thomas
>> 
>> PS: in_shutdown is an int here instead of a bool because non-fast-path
>> builds do not include stdbool. Not a good reason, of course, but I
>> wanted to keep the patch minimal and it makes no difference in practice.
>> 
>> 
>>     When using the atomic fast path deregistering can fail during
>>     program shutdown if the lookup structures are already destroyed.
>>     The assert in __deregister_frame_info_bases takes that into
>>     account. In the non-fast-path case however is not aware of
>>     program shutdown, which caused a compiler error on such platforms.
>>     We fix that by introducing a constant for in_shutdown in
>>     non-fast-path builds.
>> 
>>     libgcc/ChangeLog:
>>             * unwind-dw2-fde.c: Introduce a constant for in_shutdown
>>             for the non-fast-path case.
>> 
>> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
>> index d237179f4ea..0bcd5061d76 100644
>> --- a/libgcc/unwind-dw2-fde.c
>> +++ b/libgcc/unwind-dw2-fde.c
>> @@ -67,6 +67,8 @@ static void
>>  init_object (struct object *ob);
>> 
>>  #else
>> +/* Without fast path frame deregistration must always succeed.  */
>> +static const int in_shutdown = 0;
>> 
>>  /* The unseen_objects list contains objects that have been registered
>>     but not yet categorized in any way.  The seen_objects list has had
>> 
> 
> Thanks for the patch.  I'll let you and Jason decide which style solution
> is preferred.

This also breaks bootstrap on Darwin at least, so an early solution would be
welcome (the fix here allows bootstrap to continue, testing on-going).
thanks,
Iain

> 
> Thanks, David

Re: [PATCH] Avoid depending on destructor order

[Jeff Law]

On 9/25/22 00:29, Iain Sandoe wrote:
>
>> On 23 Sep 2022, at 15:30, David Edelsohn via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
>>
>> On Fri, Sep 23, 2022 at 10:12 AM Thomas Neumann <neumann@in.tum.de> wrote:
>>
>>>>     +static const bool in_shutdown = false;
>>>>
>>>> I'll let Jason or others decide if this is the right solution.  It seems
>>>> that in_shutdown also could be declared outside the #ifdef and
>>>> initialized as "false".
>>> sure, either is fine. Moving it outside the #ifdef wastes one byte in
>>> the executable (while the compiler can eliminate the const), but it does
>>> not really matter.
>>>
>>> I have verified that the patch below fixes builds for both fast-path and
>>> non-fast-path builds. But if you prefer I will move the in_shutdown
>>> definition instead.
>>>
>>> Best
>>>
>>> Thomas
>>>
>>> PS: in_shutdown is an int here instead of a bool because non-fast-path
>>> builds do not include stdbool. Not a good reason, of course, but I
>>> wanted to keep the patch minimal and it makes no difference in practice.
>>>
>>>
>>>      When using the atomic fast path deregistering can fail during
>>>      program shutdown if the lookup structures are already destroyed.
>>>      The assert in __deregister_frame_info_bases takes that into
>>>      account. In the non-fast-path case however is not aware of
>>>      program shutdown, which caused a compiler error on such platforms.
>>>      We fix that by introducing a constant for in_shutdown in
>>>      non-fast-path builds.
>>>
>>>      libgcc/ChangeLog:
>>>              * unwind-dw2-fde.c: Introduce a constant for in_shutdown
>>>              for the non-fast-path case.
>>>
>>> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
>>> index d237179f4ea..0bcd5061d76 100644
>>> --- a/libgcc/unwind-dw2-fde.c
>>> +++ b/libgcc/unwind-dw2-fde.c
>>> @@ -67,6 +67,8 @@ static void
>>>   init_object (struct object *ob);
>>>
>>>   #else
>>> +/* Without fast path frame deregistration must always succeed.  */
>>> +static const int in_shutdown = 0;
>>>
>>>   /* The unseen_objects list contains objects that have been registered
>>>      but not yet categorized in any way.  The seen_objects list has had
>>>
>> Thanks for the patch.  I'll let you and Jason decide which style solution
>> is preferred.
> This also breaks bootstrap on Darwin at least, so an early solution would be
> welcome (the fix here allows bootstrap to continue, testing on-going).
> thanks,

I'm using it in the automated tester as well -- without all the *-elf 
targets would fail to build libgcc.



jeff

Re: [PATCH] Avoid depending on destructor order

[Rainer Orth]

[-- Attachment #1: Type: text/plain, Size: 1255 bytes --]

Hi Jeff,

>>> Thanks for the patch.  I'll let you and Jason decide which style solution
>>> is preferred.
>> This also breaks bootstrap on Darwin at least, so an early solution would be
>> welcome (the fix here allows bootstrap to continue, testing on-going).
>> thanks,
>
> I'm using it in the automated tester as well -- without all the *-elf
> targets would fail to build libgcc.

things are even worse on targets that lack constructor priority support,
like Solaris 11.3 and Mac OS X 10.7/Darwin 11:

In file included from /vol/gcc/src/hg/master/local/libgcc/unwind-dw2-fde-dip.c:97:
/vol/gcc/src/hg/master/local/libgcc/unwind-dw2-fde.c:54:1: error: destructor priorities are not supported
   54 | release_registered_frames (void) __attribute__ ((destructor (110)));
      | ^~~~~~~~~~~~~~~~~~~~~~~~~

This is already checked for in libgcc/configure, and the situation
handled in libgcc/config/i386/cpuinfo.c.  The following patch unbroke
bootstrap on both affected targets and I saw no apparent regressions.
However, I cannot tell if the destructor priority is actually required
for correctness.

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University



[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: udf.patch --]
[-- Type: text/x-patch, Size: 637 bytes --]

diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -47,11 +47,17 @@ typedef __UINTPTR_TYPE__ uintptr_type;
 #ifdef ATOMIC_FDE_FAST_PATH
 #include "unwind-dw2-btree.h"
 
+#ifdef HAVE_INIT_PRIORITY
+#define DESTRUCTOR_PRIORITY (110)
+#else
+#define DESTRUCTOR_PRIORITY
+#endif
+
 static struct btree registered_frames;
 static bool in_shutdown;
 
 static void
-release_registered_frames (void) __attribute__ ((destructor (110)));
+release_registered_frames (void) __attribute__ ((destructor DESTRUCTOR_PRIORITY));
 static void
 release_registered_frames (void)
 {

Re: [PATCH] Avoid depending on destructor order

[Jason Merrill]

On 9/23/22 10:12, Thomas Neumann wrote:
>>
>>     +static const bool in_shutdown = false;
>>
>> I'll let Jason or others decide if this is the right solution.  It 
>> seems that in_shutdown also could be declared outside the #ifdef and 
>> initialized as "false".
> 
> sure, either is fine. Moving it outside the #ifdef wastes one byte in 
> the executable (while the compiler can eliminate the const), but it does 
> not really matter.

Might as well go with your patch, then, adding a comment to explain why 
the variable is defined in two places.

> I have verified that the patch below fixes builds for both fast-path and 
> non-fast-path builds. But if you prefer I will move the in_shutdown 
> definition instead.
> 
> Best
> 
> Thomas
> 
> PS: in_shutdown is an int here instead of a bool because non-fast-path 
> builds do not include stdbool. Not a good reason, of course, but I 
> wanted to keep the patch minimal and it makes no difference in practice.
> 
> 
>      When using the atomic fast path deregistering can fail during
>      program shutdown if the lookup structures are already destroyed.
>      The assert in __deregister_frame_info_bases takes that into
>      account. In the non-fast-path case however is not aware of
>      program shutdown, which caused a compiler error on such platforms.
>      We fix that by introducing a constant for in_shutdown in
>      non-fast-path builds.
> 
>      libgcc/ChangeLog:
>              * unwind-dw2-fde.c: Introduce a constant for in_shutdown
>              for the non-fast-path case.
> 
> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
> index d237179f4ea..0bcd5061d76 100644
> --- a/libgcc/unwind-dw2-fde.c
> +++ b/libgcc/unwind-dw2-fde.c
> @@ -67,6 +67,8 @@ static void
>   init_object (struct object *ob);
> 
>   #else
> +/* Without fast path frame deregistration must always succeed.  */
> +static const int in_shutdown = 0;
> 
>   /* The unseen_objects list contains objects that have been registered
>      but not yet categorized in any way.  The seen_objects list has had
> 

Re: [PATCH] Avoid depending on destructor order

[David Edelsohn]

[-- Attachment #1: Type: text/plain, Size: 1451 bytes --]

On Fri, Sep 23, 2022 at 9:38 AM Thomas Neumann <neumann@in.tum.de> wrote:

> > This patch broke bootstrap on AIX and probably other targets.
> >
> > #ifdef ATOMIC_FDE_FAST_PATH
> > #include "unwind-dw2-btree.h"
> >
> > static struct btree registered_frames;
> > static bool in_shutdown;
> > ...
> > #else
> >
> > in_shutdown only is defined for ATOMIC_FDE_FAST_PATH but used in code /
> > asserts not protected by that macro.
> >
> >    gcc_assert (in_shutdown || ob);
> >    return (void *) ob;
> > }
>
> I am sorry for that, I did not consider that my test machines all use
> the fast path.
>
> I think the problem can be fixed by the trivial patch below, I will
> commit that after I have tested builds both with and without fast path.
>
> Best
>
> Thomas
>
>
> diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
> index d237179f4ea..d6e347c5481 100644
> --- a/libgcc/unwind-dw2-fde.c
> +++ b/libgcc/unwind-dw2-fde.c
> @@ -67,6 +67,8 @@ static void
>   init_object (struct object *ob);
>
>   #else
> +/* Without fast path frame lookup must always succeed */
> +static const bool in_shutdown = false;
>
>   /* The unseen_objects list contains objects that have been registered
>      but not yet categorized in any way.  The seen_objects list has had
>

I tried the patch but it still failed because the type name "bool"  is not
known.  This patch is the only use of "bool" in the libgcc source code,
which is C, not C++.

Thanks, David