[PATCH] ntdll: Fix unwinding leaf functions of builtin modules in ARM/ARM64.

[Jinoh Kang]

On 12/9/21 23:28, Alexandre Julliard wrote:
> Jinoh Kang <jinoh.kang.kr at gmail.com> writes:
> 
>> Commit 5c101ed58f5 (ntdll: Fix unwinding of leaf functions on ARM64.,
>> 2019-10-23) changed the sign of UNW_ENOINFO when testing for error from
>> libunwind.  However, unw_get_proc_info() does not return a sign-flipped
>> error code.  Thus, comparing it with -UNW_ENOINFO is a no-op.
> 
> That seems specific to the LLVM version, the standalone libunwind
> definitely returns negative values:
> 
> https://github.com/libunwind/libunwind/blob/master/src/dwarf/Gparser.c#L468
> 

I just learned that libunwind functions may return *both* positive and
negative error codes.  Probably wise to test for both?

Quoting https://github.com/libunwind/libunwind/blob/a8609062849f8261a40c170941400e6ba0a499c0/include/libunwind-common.h.in#L57-L58

> /* Error codes.  The unwind routines return the *negated* values of
>    these error codes on error and a non-negative value on success.  */
> typedef enum
>   {
>     UNW_ESUCCESS = 0,		/* no error */
>     UNW_EUNSPEC,		/* unspecified (general) error */

-- 
Sincerely,
Jinoh Kang