Bugzilla bug 237183: adds an exception handler for every NSPR thread that

is created.  It also exports two functions to set and unset the exception
handler function so they can be used by the primordial thread.  The patch
is contributed by Javier Pedemonte <pedemont@us.ibm.com>. r=wtc.
Modified Files: pprthred.h os2extra.def os2thred.c

nsprpub/pr/include/private/pprthred.h

@@ -41,6 +41,12 @@
 */
 #include "nspr.h"
 
+#if defined(XP_OS2)
+#define INCL_DOS
+#define INCL_DOSERRORS
+#define INCL_WIN
+#include <os2.h>
+#endif
 
 PR_BEGIN_EXTERN_C
 
@@ -336,6 +342,16 @@ NSPR_API(void) _PR_Irix_Set_Arena_Params(PRInt32 initusers, PRInt32 initsize);
 
 #endif /* IRIX */
 
+#if defined(XP_OS2)
+/*
+** These functions need to be called at the start and end of a thread.
+** An EXCEPTIONREGISTRATIONRECORD must be declared on the stack and its
+** address passed to the two functions.
+*/
+NSPR_API(void) PR_OS2_SetFloatExcpHandler(EXCEPTIONREGISTRATIONRECORD* e);
+NSPR_API(void) PR_OS2_UnsetFloatExcpHandler(EXCEPTIONREGISTRATIONRECORD* e);
+#endif /* XP_OS2 */
+
 /* I think PR_GetMonitorEntryCount is useless. All you really want is this... */
 #define PR_InMonitor(m)		(PR_GetMonitorEntryCount(m) > 0)
 

nsprpub/pr/src/md/os2/os2thred.c

@@ -43,6 +43,8 @@
 #include <signal.h>
 #endif
 
+#include <float.h>
+
 /* --- globals ------------------------------------------------ */
 _NSPR_TLS*        pThreadLocalStorage = 0;
 _PRInterruptTable             _pr_interruptTable[] = { { 0 } };
@@ -88,6 +90,87 @@ _pr_SetThreadMDHandle(PRThread *thread)
    thread->md.handle = ptib->tib_ptib2->tib2_ultid;
 }
 
+/* On OS/2, some system function calls seem to change the FPU control word,
+ * such that we crash with a floating underflow exception.  The FIX_FPU() call
+ * in jsnum.c does not always work, as sometimes FIX_FPU() is called BEFORE the
+ * OS/2 system call that horks the FPU control word.  So, we set an exception
+ * handler that covers any floating point exceptions and resets the FPU CW to
+ * the required value.
+ */
+static ULONG
+_System OS2_FloatExcpHandler(PEXCEPTIONREPORTRECORD p1,
+                             PEXCEPTIONREGISTRATIONRECORD p2,
+                             PCONTEXTRECORD p3,
+                             PVOID pv)
+{
+#ifdef DEBUG_pedemonte
+    printf("Entering exception handler; ExceptionNum = %x\n", p1->ExceptionNum);
+    switch(p1->ExceptionNum) {
+        case XCPT_FLOAT_DENORMAL_OPERAND:
+            printf("got XCPT_FLOAT_DENORMAL_OPERAND\n");
+            break;
+        case XCPT_FLOAT_DIVIDE_BY_ZERO:
+            printf("got XCPT_FLOAT_DIVIDE_BY_ZERO\n");
+            break;
+        case XCPT_FLOAT_INEXACT_RESULT:
+            printf("got XCPT_FLOAT_INEXACT_RESULT\n");
+            break;
+        case XCPT_FLOAT_INVALID_OPERATION:
+            printf("got XCPT_FLOAT_INVALID_OPERATION\n");
+            break;
+        case XCPT_FLOAT_OVERFLOW:
+            printf("got XCPT_FLOAT_OVERFLOW\n");
+            break;
+        case XCPT_FLOAT_STACK_CHECK:
+            printf("got XCPT_FLOAT_STACK_CHECK\n");
+            break;
+        case XCPT_FLOAT_UNDERFLOW:
+            printf("got XCPT_FLOAT_UNDERFLOW\n");
+            break;
+    }
+#endif
+
+    switch(p1->ExceptionNum) {
+        case XCPT_FLOAT_DENORMAL_OPERAND:
+        case XCPT_FLOAT_DIVIDE_BY_ZERO:
+        case XCPT_FLOAT_INEXACT_RESULT:
+        case XCPT_FLOAT_INVALID_OPERATION:
+        case XCPT_FLOAT_OVERFLOW:
+        case XCPT_FLOAT_STACK_CHECK:
+        case XCPT_FLOAT_UNDERFLOW:
+        {
+            unsigned cw = p3->ctx_env[0];
+            if ((cw & MCW_EM) != MCW_EM) {
+                /* Mask out all floating point exceptions */
+                p3->ctx_env[0] |= MCW_EM;
+                /* Following two lines set precision to 53 bit mantissa.  See jsnum.c */
+                p3->ctx_env[0] &= ~MCW_PC;
+                p3->ctx_env[0] |= PC_53;
+                return XCPT_CONTINUE_EXECUTION;
+            }
+        }
+    }
+    return XCPT_CONTINUE_SEARCH;
+}
+
+PR_IMPLEMENT(void)
+PR_OS2_SetFloatExcpHandler(EXCEPTIONREGISTRATIONRECORD* excpreg)
+{
+    /* setup the exception handler for the thread */
+    APIRET rv;
+    excpreg->ExceptionHandler = OS2_FloatExcpHandler;
+    excpreg->prev_structure = NULL;
+    rv = DosSetExceptionHandler(excpreg);
+    PR_ASSERT(rv == NO_ERROR);
+}
+
+PR_IMPLEMENT(void)
+PR_OS2_UnsetFloatExcpHandler(EXCEPTIONREGISTRATIONRECORD* excpreg)
+{
+    /* unset exception handler */
+    APIRET rv = DosUnsetExceptionHandler(excpreg);
+    PR_ASSERT(rv == NO_ERROR);
+}
 
 PRStatus
 _PR_MD_INIT_THREAD(PRThread *thread)
@@ -103,6 +186,29 @@ _PR_MD_INIT_THREAD(PRThread *thread)
    return (rv == NO_ERROR) ? PR_SUCCESS : PR_FAILURE;
 }
 
+typedef struct param_store
+{
+    void (*start)(void *);
+    PRThread* thread;
+} PARAMSTORE;
+
+/* This is a small intermediate function that sets/unsets the exception
+   handler before calling the initial thread function */
+static void
+ExcpStartFunc(void* arg)
+{
+    EXCEPTIONREGISTRATIONRECORD excpreg;
+    PARAMSTORE params, *pParams = arg;
+
+    PR_OS2_SetFloatExcpHandler(&excpreg);
+
+    params = *pParams;
+    PR_Free(pParams);
+    params.start(params.thread);
+
+    PR_OS2_UnsetFloatExcpHandler(&excpreg);
+}
+
 PRStatus
 _PR_MD_CREATE_THREAD(PRThread *thread, 
                   void (*start)(void *), 
@@ -111,10 +217,13 @@ _PR_MD_CREATE_THREAD(PRThread *thread,
                   PRThreadState state, 
                   PRUint32 stackSize)
 {
-    thread->md.handle = thread->id = (TID) _beginthread(start,
+    PARAMSTORE* params = PR_Malloc(sizeof(PARAMSTORE));
+    params->start = start;
+    params->thread = thread;
+    thread->md.handle = thread->id = (TID) _beginthread(ExcpStartFunc,
                                                         NULL, 
                                                         thread->stack->stackSize,
-                                                        thread);
+                                                        params);
     if(thread->md.handle == -1) {
         return PR_FAILURE;
     }

nsprpub/pr/src/os2extra.def

@@ -8,4 +8,9 @@
     PR_GetCurrentThread
     PR_AttachThread
     PR_DetachThread
+    ;
+    ; Exception handler functions that are used by nsAppRunner.cpp
+    ;
+    _PR_OS2_SetFloatExcpHandler
+    _PR_OS2_UnsetFloatExcpHandler