#2676 [NSIS] Valid EW_SETFLAG form triggers BadCmd=13 and hides WriteUninstaller output

[sitiom]

• Issue encountered on https://github.com/ScoopInstaller/Extras/issues/15709#issue-3201696645, https://github.com/ScoopInstaller/Extras/issues/16720, etc.

7-Zip fails to list/extract the generated uninstaller from a valid NSIS 3.10+ installer when the installer uses a plug-in call before WriteUninstaller.

Reproduction

Unicode true

Name "NSIS 3.10 Uninstaller Probe"
OutFile "nsis-310-uninstaller-probe.exe"
InstallDir "$TEMP\Nsis310UninstallerProbe"
RequestExecutionLevel user

ShowInstDetails show
ShowUninstDetails show
SetCompressor /SOLID lzma

Section "Install"
  SetOutPath "$INSTDIR"

  FileOpen $0 "$INSTDIR\installed.txt" w
  FileWrite $0 "Installed by the NSIS 3.10 uninstaller probe.$\r$\n"
  FileClose $0

  SetDetailsPrint lastused
  System::Call "kernel32::GetTickCount() i.r0"
  DetailPrint "System plug-in returned $0"

  WriteUninstaller "$INSTDIR\Uninstall Probe.exe"
SectionEnd

Section "Uninstall"
  Delete "$INSTDIR\installed.txt"
  Delete "$INSTDIR\Uninstall Probe.exe"
  RMDir "$INSTDIR"
SectionEnd

makensis.exe /VERSION
makensis.exe nsis-310-uninstaller-probe.nsi
7z.exe l -slt nsis-310-uninstaller-probe.exe
7z.exe x -y -otmp-7z-nsis-310-probe nsis-310-uninstaller-probe.exe

The same minimal script works with NSIS 3.09, but when compiled with NSIS 3.10, 7-Zip reports:

Path = nsis-310-uninstaller-probe.exe
Type = Nsis
SubType = NSIS-3 Unicode BadCmd=13

Path = $PLUGINSDIR\System.dll

Expected result

7-Zip should also list/extract the generated uninstaller:

$PLUGINSDIR\System.dll
Uninstall Probe.exe

Likely Cause

7-Zip appears to treat EW_SETFLAG as having at most 3 meaningful parameters. NSIS 3.10 introduced a special SetDetailsPrint lastused / plug-in handling form that emits EW_SETFLAG with an additional parameter (NSIS-Dev/nsis@52a3b5d)

[Igor Pavlov]

Please attach test file in compiled form