fix qtfred heap corruption in FastDebug builds#7450
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FastDebug FSO compiled with /MDd (debug CRT) but imported Qt's Release
libraries via CMAKE_MAP_IMPORTED_CONFIG_FASTDEBUG = Release Debug. Qt
Release ships /MD, so any allocation crossing the qtfred <-> Qt boundary
went into one heap and came back out of the other, tripping
_CrtIsValidHeapPointer on a perfectly-valid std::string dtor. Latent for
ages because it only surfaces when an allocation actually crosses;
opening a mission file is one such path.
To paper over the resulting STL layout difference, FastDebug also forced
_ITERATOR_DEBUG_LEVEL=0 so qtfred's std::string matched Release Qt's.
Not needed once we link Debug Qt, and keeping it would introduce a fresh
mismatch (qtfred IDL=0 vs Debug Qt IDL=2).
Fix:
- Map FastDebug imports to "Debug Release \"\"" in qtfred/CMakeLists.
Debug picks Qt's debug libs; Release is a defensive fallback; the
empty entry falls back to plain IMPORTED_LOCATION, required because
Qt's host tools (uic/moc/rcc/qhelpgenerator) ship a single variant
with no IMPORTED_LOCATION_<CONFIG>. Must precede find_package(Qt5):
CMake snapshots the variable into each target's MAP_IMPORTED_CONFIG
property at creation time. (Also why the prior "Release Debug" was
silently a no-op -- set after find_package, ignored; CMake fell
back to Release on its own.)
- Extend the qwindows/qsqlite plugin POST_BUILD copies' "d"-suffix
generator expression to match FastDebug as well as Debug, so the
Debug Qt runtime finds qwindowsd.dll / qsqlited.dll alongside.
- Drop the FastDebug-only _ITERATOR_DEBUG_LEVEL=0 from the MSVC
toolchain file. Qt was the sole consumer; pure-C deps don't care.
Cost: FastDebug STL containers pick up MSVC's debug-iterator overhead.
Reasonable trade for a config named "Debug with optimizations".
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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May 11, 2026
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FastDebug FSO compiled with /MDd (debug CRT) but imported Qt's Release libraries via CMAKE_MAP_IMPORTED_CONFIG_FASTDEBUG = Release Debug. Qt Release ships /MD, so any allocation crossing the qtfred <-> Qt boundary went into one heap and came back out of the other, tripping _CrtIsValidHeapPointer on a perfectly-valid std::string dtor. Latent for ages because it only surfaces when an allocation actually crosses; opening a mission file is one such path.
To paper over the resulting STL layout difference, FastDebug also forced _ITERATOR_DEBUG_LEVEL=0 so qtfred's std::string matched Release Qt's. Not needed once we link Debug Qt, and keeping it would introduce a fresh mismatch (qtfred IDL=0 vs Debug Qt IDL=2).
Fix:
Cost: FastDebug STL containers pick up MSVC's debug-iterator overhead. Reasonable trade for a config named "Debug with optimizations".