Read a 32-bit process's command line from a 64-bit host - #798
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NtQueryInformationProcess with ProcessBasicInformation answers a 64-bit caller with the 64-bit PEB, even when the target runs under WOW64. GetCommandLine then handed that address to ReadCommandLine32, which reads it with 32-bit offsets and gets nothing usable. So no 32-bit diff tool ever had a command line - and that is most of them, since %ProgramFiles(x86)% is where the resolver goes looking. The consequences are the two things a command line is for: such a tool was never seen as already running, so AutoRefresh opened a second window instead of reusing the first and every relaunch spent another MaxInstance slot, and Kill never matched it, so it was never closed. Ask for the 32-bit PEB by name, through ProcessWow64Information. Also return null rather than a misread when a 32-bit host looks at a 64-bit target, which is the same confusion the other way round and equally unreadable. The test starts SysWOW64\cmd.exe, shaped like a diff tool invocation so FindAll keeps it, and looks for its command line. It fails without the fix.
This was referenced Aug 26, 2026
This was referenced Aug 27, 2026
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NtQueryInformationProcess with ProcessBasicInformation answers a 64-bit caller
with the 64-bit PEB, even when the target runs under WOW64. GetCommandLine then
handed that address to ReadCommandLine32, which reads it with 32-bit offsets and
gets nothing usable.
So no 32-bit diff tool ever had a command line - and that is most of them, since
%ProgramFiles(x86)% is where the resolver goes looking. The consequences are the
two things a command line is for: such a tool was never seen as already running,
so AutoRefresh opened a second window instead of reusing the first and every
relaunch spent another MaxInstance slot, and Kill never matched it, so it was
never closed.
Ask for the 32-bit PEB by name, through ProcessWow64Information. Also return
null rather than a misread when a 32-bit host looks at a 64-bit target, which is
the same confusion the other way round and equally unreadable.
The test starts SysWOW64\cmd.exe, shaped like a diff tool invocation so FindAll
keeps it, and looks for its command line. It fails without the fix.