Changeset 1111

Timestamp:

Feb 28, 2013, 11:47:15 PM (12 years ago)

Author:

Dmitry A. Kuminov

Message:

corelib: Make sure QLibrary::load() doesn't change FPU control word.

This is known to happen on OS/2 when loading some DLLs and it causes
applications to unexpectedly crash with SIGFPE when doing some FPU
arithmetics (like division by zero).

File:

• trunk/src/corelib/plugin/qlibrary_os2.cpp (modified) (3 diffs)

trunk/src/corelib/plugin/qlibrary_os2.cpp

@@ -48 +48 @@
 #include "qfileinfo.h"
 #include "qdir.h"
+
+#include <float.h>
 
 #ifndef QT_NO_LIBRARY
@@ -100 +102 @@
     QByteArray attempt = QFile::encodeName(QDir::toNativeSeparators(fileName));
 
+    // It is known that the OS/2 DLL loader (or the init routine of some DLLs)
+    // sometimes resets the FPU CW to a value that causes operations like
+    // division by zero to throw SIGFPE instead of being handled by the FPU.
+    // This is unexpected in many apps since they rely on the default C runtime
+    // setting which is to handle them. The solution is to force the required
+    // CW value and then restore it after loading the DLL.
+
+    _clear87();
+    unsigned int oldbits = _control87(0, 0);
+    _control87(MCW_EM, MCW_EM);
+
     APIRET rc;
     char errModule[CCHMAXPATH] = { '\0' };
@@ -108 +121 @@
         rc = DosLoadModule(errModule, sizeof(errModule), attempt, &pHnd);
     }
+
+    _clear87();
+    _control87(oldbits, 0xFFFFF);
 
     if (rc != NO_ERROR) {