From: Rudolf Polzer <[email protected]>
The previous implementation read 4097 bytes, but always cleared the
4097th byte - so whenever the engine had more than 4096 bytes to send,
one byte will get spuriously zeroed out, leading to lichess-bot
complaining about `inf\x00` being an undefined UCI command and similar
things.
In theory this can even lead to the engine timing out and losing a game
as the UCI command with the actual move has been corrupted, but I have
never observed that happen.
As here all data corruption happens within the buffer, this cannot be
reproduced with AddressSanitizer.
---
src/frontend/engine.cc | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/src/frontend/engine.cc b/src/frontend/engine.cc
index e8fb3a2..cb7d974 100644
--- a/src/frontend/engine.cc
+++ b/src/frontend/engine.cc
@@ -551,7 +551,7 @@ void ForwardEngineOutputToUser( void )
fd_set set[1];
struct timeval time_val[1];
int engineinputready=0;
- char engineinputaux[BUF_SIZE+1]="";
+ char engineinputaux[BUF_SIZE]="";
/* Poll input from engine in non-blocking mode */
FD_ZERO(set);
@@ -564,15 +564,13 @@ void ForwardEngineOutputToUser( void )
printf( "Error reading engine input.\n" );
} else if ( engineinputready > 0 ) {
/* There are some data from the engine. Read the data */
- strncpy( engineinputaux, zerochar, BUF_SIZE+1 );
- nread = read( pipefd_e2a[0], engineinputaux, BUF_SIZE+1 );
- /* Write data to output */
- assert( nread <= BUF_SIZE+1 );
- if (nread < BUF_SIZE+1) {
- engineinputaux[nread] = '\0';
- } else {
- engineinputaux[BUF_SIZE] = '\0';
+ nread = read( pipefd_e2a[0], engineinputaux, BUF_SIZE );
+ if ( nread == -1 ) {
+ printf( "Error reading message from engine.\n" );
+ return;
}
+ /* Write data to output */
+ assert( nread <= BUF_SIZE );
ssize_t r = write( STDOUT_FILENO, engineinputaux, nread );
if ( r == -1 ) {
printf( "Error sending message to engine.\n" );
--
2.39.5
