[PATCH] ntdll: Truncate and ellipsize debug output if it's too long.

[Esme Povirk]

Signed-off-by: Esme Povirk <esme at codeweavers.com>
---
It turns out that, in addition to Mono's debug output being too long
sometimes, one can trigger an overrun by passing too many arguments
to a managed exe while the +mscoree debug channel is enabled. To
guarantee that this won't happen in mscoree, we would either have to
limit the number of arguments traced to 2 (since debug output for the
filename and each argument could be up to 300 characters, and it
needs to fit in a 1020 character buffer) or keep track of the lengths
from each call to debugstr_w.

I don't think there's any reasonable way for callers to ensure that
in general we won't overrun this buffer, and losing some debug
output on occasion is much better than crashing.

 dlls/ntdll/thread.c     | 10 +++++-----
 dlls/ntdll/unix/debug.c |  8 +++++---
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/dlls/ntdll/thread.c b/dlls/ntdll/thread.c
index 37dc7c8ab37..17e9cc0bf98 100644
--- a/dlls/ntdll/thread.c
+++ b/dlls/ntdll/thread.c
@@ -74,11 +74,11 @@ static int append_output( struct debug_info *info, const char *str, size_t len )
 {
     if (len >= sizeof(info->output) - info->out_pos)
     {
-        __wine_dbg_write( info->output, info->out_pos );
-        info->out_pos = 0;
-        ERR_(thread)( "debug buffer overflow:\n" );
-        __wine_dbg_write( str, len );
-        RtlRaiseStatus( STATUS_BUFFER_OVERFLOW );
+        len = sizeof(info->output) - info->out_pos;
+        memcpy( info->output + info->out_pos, str, len );
+        memcpy( info->output + sizeof(info->output) - 4, "...\n", 4 );
+        info->out_pos = sizeof(info->output);
+        return len;
     }
     memcpy( info->output + info->out_pos, str, len );
     info->out_pos += len;
diff --git a/dlls/ntdll/unix/debug.c b/dlls/ntdll/unix/debug.c
index d43cdaeb917..e435a58aa12 100644
--- a/dlls/ntdll/unix/debug.c
+++ b/dlls/ntdll/unix/debug.c
@@ -78,9 +78,11 @@ static int append_output( struct debug_info *info, const char *str, size_t len )
 {
     if (len >= sizeof(info->output) - info->out_pos)
     {
-       fprintf( stderr, "wine_dbg_output: debugstr buffer overflow (contents: '%s')\n", info->output );
-       info->out_pos = 0;
-       abort();
+        len = sizeof(info->output) - info->out_pos;
+        memcpy( info->output + info->out_pos, str, len );
+        memcpy( info->output + sizeof(info->output) - 4, "...\n", 4 );
+        info->out_pos = sizeof(info->output);
+        return len;
     }
     memcpy( info->output + info->out_pos, str, len );
     info->out_pos += len;
-- 
2.25.1