How to use alias interpreter inside another alias in WinDbg?

I have a bunch of aliases for accessing global debug variables in my code, which look something like this:

aS _dbg_log_last "dx mymodule!g_dbg_variable_with_a_long_name->logger.log_buffer[mymodule!g_dbg_variable_with_a_long_name->logger.size - 1]"

I am obviously not a fan of the last one with the repetition, so I tried to refactor it to the following:

aS _dbg_log "mymodule!g_dbg_variable_with_a_long_name->logger"
aS _dbg_log_last "dx ${_dbg_log} .log_buffer[${_dbg_log}.size - 1]"

If I copy the contents of the _dbg_log_last alias and run it manually, everything works. But if I actually try to invoke it, I am getting an error:

Error: unexpected token at {_dbg_log}...

So it look like it swallow the $ character when executing the alias. I have tried also unquoting either or both aliases, using as instead of aS, adding /f and other flags to alias interpreter, escaping the $ with \$ or $$, nothing works.

Minimal repro:

aS _foo "1"
aS _bar "dx ${_foo} ,x"

dx ${_foo} ,x
_bar

Expected:

1 ,x : 0x1
1 ,x : 0x1

Actual:

1 ,x : 0x1
Error: Unexpected token at '{_foo} ,x'

Solution

As Nietsa says mixing dx with as / aS may not be compatible

but unless you force execute with a .block{} the aliases are not going to be expanded

ill show an example with a public struct see if that helps you

delete prior aliases if any and list

0:000> ad *
0:000> al
No aliases

define new alaises and list

0:000> as foo ((ntdll!_PEB *)@$proc)->ProcessParameters
0:000> as bar ${foo}->DesktopInfo
0:000> al
  Alias            Value
 -------          -------
 bar              ${foo}->DesktopInfo
 foo              ((ntdll!_PEB *)@$proc)->ProcessParameters

check the simple alias

0:000> ?? ${foo}->WindowTitle
struct _UNICODE_STRING
 "C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\cdb.exe"
   +0x000 Length           : 0x78
   +0x002 MaximumLength    : 0x7a
   +0x008 Buffer           : 0x000002c3`30ca2e3a  "C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\cdb.exe"

check the compound alias without a surrounding .block{}

0:000> ?? ${bar}
Unexpected character in '${foo}->DesktopInfo'

surround it with a .block to force expansion first

0:000> .block { ?? ${bar} }
struct _UNICODE_STRING
 "WinSta0\Default"
   +0x000 Length           : 0x1e
   +0x002 MaximumLength    : 0x20
   +0x008 Buffer           : 0x000002c3`30ca2eb4  "WinSta0\Default"
0:000>

supposedly if you have a script file that is based on foo and bar above as below

.block { ?? ${bar}.Buffer[0] }
.block { ?? ${bar}.Buffer[1] }
.block { ?? ${bar}.Buffer[2] }
.block { ?? ${bar}.Buffer[3] }
.block { ?? ${bar}.Buffer[4] }
.block { ?? ${bar}.Buffer[5] }
.block { ?? ${bar}.Buffer[6] == '1' } 
.block { ?? ${bar}.Buffer[6] == '0' }

running the script should yield

0:000> $$>< d:\alias.wds
wchar_t 0x57 'W'
wchar_t 0x69 'i'
wchar_t 0x6e 'n'
wchar_t 0x53 'S'
wchar_t 0x74 't'
wchar_t 0x61 'a'
bool false
bool true
0:000>