Allow trimming of TerminalFormatStrings - #132597

src/libraries/System.Console/src/System/ConsolePal.Unix.cs:39

• s_invalidateCachedSettings is typed as bool, but this code uses Interlocked.CompareExchange(ref s_invalidateCachedSettings, ...). In this repo, Interlocked.CompareExchange has overloads for byte, short, etc., but not for bool, so the current code will not compile. Use a byte sentinel (0/1) as requested in the review thread and adjust the initializer accordingly.

        private static bool s_invalidateCachedSettings = true; // Tracks whether we should invalidate the cached settings.

src/libraries/System.Console/src/System/ConsolePal.Unix.cs:1108

• Interlocked.CompareExchange doesn't support bool in this repo, so this call won't compile once s_invalidateCachedSettings is changed to a byte sentinel. Update the CompareExchange call to use 0/1 and compare the returned previous value.

            bool invalidateSettings = Interlocked.CompareExchange(ref s_invalidateCachedSettings, false, true);

src/libraries/System.Console/src/System/ConsolePal.Unix.cs:1119

• This write should match the atomic flag type used by CheckTerminalSettingsInvalidated. With a byte sentinel flag, write 1 (true) to trigger invalidation.

            Volatile.Write(ref s_invalidateCachedSettings, true);

src/libraries/System.Console/src/System/ConsolePal.Unix.cs:43

• s_terminalFormatStringsInstance is initialized via Interlocked.CompareExchange, but the fast-path read in TerminalFormatStringsInstance is a plain field read. For cross-thread publication on weak memory models, use Volatile.Read (this file already follows that pattern for s_stdInReader).

        public static TerminalFormatStrings TerminalFormatStringsInstance => s_terminalFormatStringsInstance ?? Initialize();

src/libraries/System.Console/src/System/ConsolePal.Unix.cs:46

• TerminalFormatStringsInstance uses the new field backing storage plus an inline Interlocked.CompareExchange(ref field, new TerminalFormatStrings(...), null) pattern. This has two concrete problems:

1. The new TerminalFormatStrings(...) allocation happens whenever the first field read returns null, even if another thread has already initialized the instance (stale/non-volatile read), causing avoidable allocations.
2. After initialization, reads are plain (non-Volatile.Read) loads, which doesn’t provide an acquire barrier for safe publication on weaker memory models.

In this file you already use the safer pattern for s_stdInReader (Volatile.Read + CompareExchange). Consider switching this property to the same pattern with an explicit nullable backing field.

        public static TerminalFormatStrings TerminalFormatStringsInstance =>
            field ??
            Interlocked.CompareExchange(ref field, new TerminalFormatStrings(TermInfo.DatabaseFactory.ReadActiveDatabase()), null) ??
            field;