[glib: 3/7] W32: Remove allocations from the crash handler

[Philip Withnall <pwithnall src gnome org>]

commit 6d9c3e3226c8953c90bb72befe6b5d4845e14c98
Author: Руслан Ижбулатов <lrn1986 gmail com>
Date:   Tue Apr 6 11:03:45 2021 +0000

    W32: Remove allocations from the crash handler
    
    Use OutputDebugStringA() instead of fprintf.
    
    The goal for this code is to inform the person running the debugger
    about the exception that caused the debugger to be attached.
    This is useful for debugging with gdb, because gdb does not catch Windows
    exception information (it just displays "Segmentation fault").
    
    OutputDebugStringA() ensures that the output goes to the debugger,
    and the (ab)use of strcpy() with a stack-allocated buffer ensures
    that we do not allocate anything while the crash handler is running,
    nor to we call CRT functions that can be reasinably expected to allocate
    anything.

 glib/gwin32.c | 122 ++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 84 insertions(+), 38 deletions(-)
---
diff --git a/glib/gwin32.c b/glib/gwin32.c
index 657b18e3e..8d29f376a 100644
--- a/glib/gwin32.c
+++ b/glib/gwin32.c
@@ -1049,6 +1049,24 @@ static DWORD        debugger_spawn_flags = 0;
 
 #include "gwin32-private.c"
 
+static char *
+copy_chars (char       *buffer,
+            gsize      *buffer_size,
+            const char *to_copy)
+{
+  gsize copy_count = strlen (to_copy);
+  if (copy_count <= *buffer_size)
+    memset (buffer, 0x20, copy_count);
+  else
+    memset (buffer, 0x20, *buffer_size);
+  strncpy_s (buffer, *buffer_size, to_copy, copy_count);
+  if (*buffer_size >= copy_count)
+    *buffer_size -= copy_count;
+  else
+    *buffer_size = 0;
+  return &buffer[copy_count];
+}
+
 /* Handles exceptions (useful for debugging).
  * Issues a DebugBreak() call if the process is being debugged (not really
  * useful - if the process is being debugged, this handler won't be invoked
@@ -1092,10 +1110,17 @@ g_win32_veh_handler (PEXCEPTION_POINTERS ExceptionInfo)
   gsize                i;
   STARTUPINFOA         si;
   PROCESS_INFORMATION  pi;
+#define ITOA_BUFFER_SIZE 100
+  char                 itoa_buffer[ITOA_BUFFER_SIZE];
+#define DEBUG_STRING_SIZE 1024
+  gsize                dbgs = DEBUG_STRING_SIZE;
+  char                 debug_string[DEBUG_STRING_SIZE];
+  char                *dbgp;
 
   if (ExceptionInfo == NULL ||
       ExceptionInfo->ExceptionRecord == NULL ||
-      IsDebuggerPresent ())
+      IsDebuggerPresent () ||
+      debugger[0] == 0)
     return EXCEPTION_CONTINUE_SEARCH;
 
   er = ExceptionInfo->ExceptionRecord;
@@ -1117,43 +1142,6 @@ g_win32_veh_handler (PEXCEPTION_POINTERS ExceptionInfo)
       break;
     }
 
-  fprintf_s (stderr,
-             "Exception code=0x%lx flags=0x%lx at 0x%p",
-             er->ExceptionCode,
-             er->ExceptionFlags,
-             er->ExceptionAddress);
-
-  switch (er->ExceptionCode)
-    {
-    case EXCEPTION_ACCESS_VIOLATION:
-      fprintf_s (stderr,
-                 ". Access violation - attempting to %s at address 0x%p\n",
-                 er->ExceptionInformation[0] == 0 ? "read data" :
-                 er->ExceptionInformation[0] == 1 ? "write data" :
-                 er->ExceptionInformation[0] == 8 ? "execute data" :
-                 "do something bad",
-                 (void *) er->ExceptionInformation[1]);
-      break;
-    case EXCEPTION_IN_PAGE_ERROR:
-      fprintf_s (stderr,
-                 ". Page access violation - attempting to %s at address 0x%p with status %Ix\n",
-                 er->ExceptionInformation[0] == 0 ? "read from an inaccessible page" :
-                 er->ExceptionInformation[0] == 1 ? "write to an inaccessible page" :
-                 er->ExceptionInformation[0] == 8 ? "execute data in page" :
-                 "do something bad with a page",
-                 (void *) er->ExceptionInformation[1],
-                 er->ExceptionInformation[2]);
-      break;
-    default:
-      fprintf_s (stderr, "\n");
-      break;
-    }
-
-  fflush (stderr);
-
-  if (debugger[0] == 0)
-    return EXCEPTION_CONTINUE_SEARCH;
-
   memset (&si, 0, sizeof (si));
   memset (&pi, 0, sizeof (pi));
   si.cb = sizeof (si);
@@ -1170,6 +1158,64 @@ g_win32_veh_handler (PEXCEPTION_POINTERS ExceptionInfo)
        * event signalling.
        */
       WaitForSingleObject (debugger_wakeup_event, 60000);
+
+      dbgp = &debug_string[0];
+
+      dbgp = copy_chars (dbgp, &dbgs, "Exception code=0x");
+      itoa_buffer[0] = 0;
+      _ui64toa_s (er->ExceptionCode, itoa_buffer, ITOA_BUFFER_SIZE, 16);
+      dbgp = copy_chars (dbgp, &dbgs, itoa_buffer);
+      dbgp = copy_chars (dbgp, &dbgs, " flags=0x");
+      itoa_buffer[0] = 0;
+      _ui64toa_s (er->ExceptionFlags, itoa_buffer, ITOA_BUFFER_SIZE, 16);
+      dbgp = copy_chars (dbgp, &dbgs, itoa_buffer);
+      dbgp = copy_chars (dbgp, &dbgs, " at 0x");
+      itoa_buffer[0] = 0;
+      _ui64toa_s ((guintptr) er->ExceptionAddress, itoa_buffer, ITOA_BUFFER_SIZE, 16);
+      dbgp = copy_chars (dbgp, &dbgs, itoa_buffer);
+
+      switch (er->ExceptionCode)
+        {
+        case EXCEPTION_ACCESS_VIOLATION:
+          dbgp = copy_chars (dbgp, &dbgs, ". Access violation - attempting to ");
+          if (er->ExceptionInformation[0] == 0)
+            dbgp = copy_chars (dbgp, &dbgs, "read data");
+          else if (er->ExceptionInformation[0] == 1)
+            dbgp = copy_chars (dbgp, &dbgs, "write data");
+          else if (er->ExceptionInformation[0] == 8)
+            dbgp = copy_chars (dbgp, &dbgs, "execute data");
+          else
+            dbgp = copy_chars (dbgp, &dbgs, "do something bad");
+          dbgp = copy_chars (dbgp, &dbgs, " at address 0x");
+          itoa_buffer[0] = 0;
+          _ui64toa_s (er->ExceptionInformation[1], itoa_buffer, ITOA_BUFFER_SIZE, 16);
+          dbgp = copy_chars (dbgp, &dbgs, itoa_buffer);
+          break;
+        case EXCEPTION_IN_PAGE_ERROR:
+          dbgp = copy_chars (dbgp, &dbgs, ". Page access violation - attempting to ");
+          if (er->ExceptionInformation[0] == 0)
+            dbgp = copy_chars (dbgp, &dbgs, "read from an inaccessible page");
+          else if (er->ExceptionInformation[0] == 1)
+            dbgp = copy_chars (dbgp, &dbgs, "write to an inaccessible page");
+          else if (er->ExceptionInformation[0] == 8)
+            dbgp = copy_chars (dbgp, &dbgs, "execute data in page");
+          else
+            dbgp = copy_chars (dbgp, &dbgs, "do something bad with a page");
+          dbgp = copy_chars (dbgp, &dbgs, " at address 0x");
+          itoa_buffer[0] = 0;
+          _ui64toa_s (er->ExceptionInformation[1], itoa_buffer, ITOA_BUFFER_SIZE, 16);
+          dbgp = copy_chars (dbgp, &dbgs, itoa_buffer);
+          dbgp = copy_chars (dbgp, &dbgs, " with status ");
+          itoa_buffer[0] = 0;
+          _ui64toa_s (er->ExceptionInformation[2], itoa_buffer, ITOA_BUFFER_SIZE, 16);
+          dbgp = copy_chars (dbgp, &dbgs, itoa_buffer);
+          break;
+        default:
+          break;
+        }
+
+      dbgp = copy_chars (dbgp, &dbgs, "\n");
+      OutputDebugStringA (debug_string);
     }
 
   /* Now the debugger is present, and we can try