https://gitlab.synchro.net/main/sbbs/-/commit/ed0977a8dff6636e4c27074f
Modified Files:
src/sbbs3/ctrl/sbbsctrl.cpp
Log Message:
sbbsctrl: install a large-address-safe heap manager (GitLab #1185)

C++Builder 6's classic memory manager is not fully large-address safe.
It indexes its free-list buckets with signed size arithmetic (an arithmetic-shift divide-by-4) that only goes wrong once the heap arena
lives above 0x80000000. Since arrivals-24-among (37d2d5a6a0) built sbbsctrl.exe /LARGEADDRESSAWARE, and with Windows serving allocations
top-down, the Borland arena clusters near ~0xFD000000; a high pointer eventually lands in a block-size header, the manager masks it to a ~2GB
"size", walks past the end of the arena into freed address space, and
faults. The crash is an access violation deep in the Borland RTL,
reached via any innocent alloc/free (a server's log callback appending
to the GUI, in the observed dumps) - three occurrences on 2026-07-16,
-18 and -19, the last a WER dump whose stored context localized the
fault to the memory manager's own block-chain walk.

Rather than revert LAA and give back the 4GB the original mozjs185 heap-exhaustion crash needs, replace the manager with a thin shim over
the Windows heap (HeapAlloc/HeapReAlloc/HeapFree on GetProcessHeap()),
which is large-address safe by construction. It is installed first
thing in WinMain; the previous Borland manager is saved and chained for
any block that predates the swap, so every block is freed by the manager
that allocated it. Each of our blocks carries an 8-byte prefix holding
a magic word and a self-pointer, making foreign-block detection collision-proof. Post-install allocation churn goes to the OS heap and
never touches the buggy walker; LAA stays on (build.bat still flips the
PE bit).

Tested: sbbsctrl soaked under real load (web server served ~18K clients)
with system-wide top-down allocation active - the configuration that
provoked all three prior faults - with no crash.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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