Take care of our own error messages

1 files changed, 64 insertions, 46 deletions

diff --git a/dlfcn.c b/dlfcn.c
index c279897..4c82304 100644
--- a/dlfcn.c
+++ b/dlfcn.c
@@ -66,8 +66,13 @@ static void global_object_rem( HMODULE hModule )
     }

 }

 

-/* Argument to last function. Used in dlerror( ) */

-static char last_name[MAX_PATH];

+/* POSIX says dlerror( ) doesn't have to be thread-safe, so we use one

+ * static buffer.

+ * MSDN says the buffer cannot be larger than 64K bytes, so we set it to

+ * the limit.

+ */

+static char error_buffer[65535];

+static int dlerror_was_last_call;

 

 static int copy_string( char *dest, int dest_size, const char *src )

 {

@@ -89,19 +94,55 @@ static int copy_string( char *dest, int dest_size, const char *src )
     return i;

 }

 

+static void save_err_str( const char *str )

+{

+    DWORD dwMessageId;

+    DWORD pos;

+

+    dwMessageId = GetLastError( );

+

+    if( dwMessageId == 0 )

+        return;

+

+    /* Format error message to:

+     * "<argument to function that failed>": <Windows localized error message>

+     */

+    pos  = copy_string( error_buffer,     sizeof(error_buffer),     "\"" );

+    pos += copy_string( error_buffer+pos, sizeof(error_buffer)-pos, str );

+    pos += copy_string( error_buffer+pos, sizeof(error_buffer)-pos, "\": " );

+    pos += FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM, NULL, dwMessageId,

+                          MAKELANGID( LANG_NEUTRAL, SUBLANG_DEFAULT ),

+                          error_buffer+pos, sizeof(error_buffer)-pos, NULL );

+

+    if( pos > 1 )

+    {

+        /* POSIX says the string must not have trailing <newline> */

+        if( error_buffer[pos-2] == '\r' && error_buffer[pos-1] == '\n' )

+            error_buffer[pos-2] = '\0';

+    }

+}

+

+static void save_err_ptr( const void *ptr )

+{

+    char ptr_buf[19]; /* 0x<pointer> up to 64 bits. */

+

+    sprintf( ptr_buf, "0x%p", ptr );

+

+    save_err_str( ptr_buf );

+}

+

 void *dlopen( const char *file, int mode )

 {

     HMODULE hModule;

     UINT uMode;

 

+    dlerror_was_last_call = 0;

+

     /* Do not let Windows display the critical-error-handler message box */

     uMode = SetErrorMode( SEM_FAILCRITICALERRORS );

 

     if( file == 0 )

     {

-        /* Save NULL pointer for error message */

-        sprintf( last_name, "0x%p", file );

-

         /* POSIX says that if the value of file is 0, a handle on a global

          * symbol object must be provided. That object must be able to access

          * all symbols from the original program file, and any objects loaded

@@ -111,6 +152,9 @@ void *dlopen( const char *file, int mode )
          * the RTLD_GLOBAL flag, we create our own list later on.

          */

         hModule = GetModuleHandle( NULL );

+

+        if( !hModule )

+            save_err_ptr( file );

     }

     else

     {

@@ -129,9 +173,6 @@ void *dlopen( const char *file, int mode )
         }

         lpFileName[i] = '\0';

 

-        /* Save file name for error message */

-        copy_string( last_name, sizeof(last_name), lpFileName );

-

         /* POSIX says the search path is implementation-defined.

          * LOAD_WITH_ALTERED_SEARCH_PATH is used to make it behave more closely

          * to UNIX's search paths (start with system folders instead of current

@@ -147,7 +188,9 @@ void *dlopen( const char *file, int mode )
          * RTLD_GLOBAL, even if any further invocations use RTLD_LOCAL, the

          * symbols will remain global.

          */

-        if( hModule && (mode & RTLD_GLOBAL) )

+        if( !hModule )

+            save_err_str( lpFileName );

+        else if( (mode & RTLD_GLOBAL) )

             global_object_add( hModule );

     }

 

@@ -162,8 +205,7 @@ int dlclose( void *handle )
     HMODULE hModule = (HMODULE) handle;

     BOOL ret;

 

-    /* Save handle for error message */

-    sprintf( last_name, "0x%p", handle );

+    dlerror_was_last_call = 0;

 

     ret = FreeLibrary( hModule );

 

@@ -172,6 +214,8 @@ int dlclose( void *handle )
      */

     if( ret )

         global_object_rem( hModule );

+    else

+        save_err_ptr( handle );

 

     /* dlclose's return value in inverted in relation to FreeLibrary's. */

     ret = !ret;

@@ -183,8 +227,7 @@ void *dlsym( void *handle, const char *name )
 {

     FARPROC symbol;

 

-    /* Save symbol name for error message */

-    copy_string( last_name, sizeof(last_name), name );

+    dlerror_was_last_call = 0;

 

     symbol = GetProcAddress( handle, name );

 

@@ -216,46 +259,21 @@ void *dlsym( void *handle, const char *name )
         CloseHandle( hModule );

     }

 

+    if( symbol == NULL )

+        save_err_str( name );

+

     return (void*) symbol;

 }

 

 char *dlerror( void )

 {

-    DWORD dwMessageId;

-    /* POSIX says this function doesn't have to be thread-safe, so we use one

-     * static buffer.

-     * MSDN says the buffer cannot be larger than 64K bytes, so we set it to

-     * the limit.

-     */

-    static char lpBuffer[65535];

-    DWORD ret;

-

-    dwMessageId = GetLastError( );

-

-    if( dwMessageId == 0 )

-        return NULL;

-

-    /* Format error message to:

-     * "<argument to function that failed>": <Windows localized error message>

-     */

-    ret  = copy_string( lpBuffer, sizeof(lpBuffer), "\"" );

-    ret += copy_string( lpBuffer+ret, sizeof(lpBuffer)-ret, last_name );

-    ret += copy_string( lpBuffer+ret, sizeof(lpBuffer)-ret, "\": " );

-    ret += FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM, NULL, dwMessageId,

-                          MAKELANGID( LANG_NEUTRAL, SUBLANG_DEFAULT ),

-                          lpBuffer+ret, sizeof(lpBuffer)-ret, NULL );

-

-    if( ret > 1 )

-    {

-        /* POSIX says the string must not have trailing <newline> */

-        if( lpBuffer[ret-2] == '\r' && lpBuffer[ret-1] == '\n' )

-            lpBuffer[ret-2] = '\0';

-    }

-

     /* POSIX says that invoking dlerror( ) a second time, immediately following

      * a prior invocation, shall result in NULL being returned.

      */

-    SetLastError(0);

+    if( dlerror_was_last_call )

+        return NULL;

+

+    dlerror_was_last_call = 1;

 

-    return lpBuffer;

+    return error_buffer;

 }