main: make /gen actually mine (#42)

nMineMode defaults to MINE_RELAY (0) and ParseStartupArguments() never changed
it, so a node started with /gen would spawn ThreadBitcoinMiner, enter
BitcoinMiner(), hit

    if (nMineMode == MINE_RELAY)
        return true;

and return before doing any work. The node then ran indefinitely looking
completely healthy -- it synced, it held peers, it reported no errors -- while
earning nothing. Nothing in the log said otherwise; the only hint was
`nMineMode = 0` in a startup line that reads like a status echo.

This affects every headless miner, because the GUI is the only other way to
select a mining mode.

/gen now implies MINE_SOLO unless /operator or /participant asked for something
else. Verify with `nMineMode = 1` at startup.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index a94d01d..c64dca9 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -79,7 +79,15 @@ static void ParseStartupArguments(int argc, char* argv[])
         fDebug = true;
 
     if (arg(argc,argv,"/gen") || arg(argc,argv,"-gen"))
+    {
         fGenerateBitcoins = 1;
+        // Mining mode defaults to MINE_RELAY, and nothing in this parser ever
+        // changed it, so BitcoinMiner() returned immediately at its relay guard
+        // and /gen mined nothing at all. /operator and /participant still set
+        // their own mode below, so only the unqualified case is affected.
+        if (nMineMode == MINE_RELAY)
+            nMineMode = MINE_SOLO;
+    }
 
     if (arg(argc,argv,"/solomine") || arg(argc,argv,"-solomine"))
         fSoloMineTest = true;