RE: [PATCH v11 03/10] gdb: handle stepping through functions with DW_AT_trampoline

["Ijaz, Abdul B" <abdul.b.ijaz@intel.com>]

Thanks Tom, for the feedback.

Please see the inline reply below:

>> +/* Maximum size of trampoline chain to process while resolving
>> +   trampolines.  This avoids infinite loops for malformed debug
>> +   information.  */
>> +#define MAX_TRAMPOLINE_CHAIN_SIZE 10

Tom> Are there cases where there may be multiple trampolines chained together?
Tom> If it's unusual or pathological then I guess some hard-coded limit seems fine.
Tom> If it's normal then why 10?  Like, I'm wondering if perhaps some other approach should be taken.

Abdul> It is unusual.  A chain means a trampoline whose target is itself a trampoline; the test covers a chain of two (chained_trampoline -> trampoline -> target in gdb.dwarf2/dw2-function-trampolines.c), and I am not aware of compilers emitting longer ones.  Normally a trampoline directly calls its target.

The limit is only a safeguard, so that malformed debug information, e.g. two trampolines naming each other as target, cannot make GDB loop forever.  10 is well above what is expected in practice, so I would like to keep it as it is.

Best Regards,
Abdul Basit

-----Original Message-----
From: Tom Tromey <tom@tromey.com> 
Sent: Wednesday, October 21, 2026 10:39 PM
To: Ijaz, Abdul B <abdul.b.ijaz@intel.com>
Cc: gdb-patches@sourceware.org; JiniSusan.George@amd.com; tom@tromey.com; eliz@gnu.org; Nils-Christian Kempke <nils-christian.kempke@intel.com>
Subject: Re: [PATCH v11 03/10] gdb: handle stepping through functions with DW_AT_trampoline

>>>>> Abdul Basit Ijaz <abdul.b.ijaz@intel.com> writes:

> This patch makes infrun continue stepping into and through trampoline 
> functions marked via the DW_AT_trampoline in DWARF.

I'm probably not the best person to review this but I did have one
question:

> diff --git a/gdb/infrun.h b/gdb/infrun.h index 
> cbc603b74ed..135d1fc350b 100644
> --- a/gdb/infrun.h
> +++ b/gdb/infrun.h
 
> +/* Maximum size of trampoline chain to process while resolving
> +   trampolines.  This avoids infinite loops for malformed debug
> +   information.  */
> +#define MAX_TRAMPOLINE_CHAIN_SIZE 10

Are there cases where there may be multiple trampolines chained together?

If it's unusual or pathological then I guess some hard-coded limit seems fine.

If it's normal then why 10?  Like, I'm wondering if perhaps some other approach should be taken.

Tom
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