TIP: | 128 |
Title: | Ability to Install a Custom Memory Allocator |
Version: | $Revision: 1.5 $ |
Authors: |
Christophe Cap <udragon at users dot sourceforge dot net> Mike Jackson <hhyJackson1275 at who-got-mail dot com> |
State: | Rejected |
Type: | Project |
Tcl-Version: | 8.6 |
Vote: | Done |
Created: | Thursday, 13 March 2003 |
This TIP alters Tcl to allow embedded uses of the Tcl library (and any extensions) to either use the Tcl memory allocators as their main allocator (especially in C++) or to set the memory allocator that Tcl uses for itself through ckalloc().
A while ago I was experiencing troubles when allocating images ([image create photo]) while memory was already exhausted, my app crashed (due to known bug item #698571, which is in the HEAD by now!) This shouldn't happen anyway since my application had it's new handler set.
Tracing down the source of the allocators I noticed that Tcl uses HeapAlloc() (on Win32) to allocate its memory. Why not use malloc()?
It would be nice to be able to catch memory allocation errors with a custom new handler.
A solution could be to replace HeapAlloc() (on Win32) and other platform specific memory handlers should be replaced by malloc().
This way a new handler can by set through set_new_handler().
Note that the Microsoft VC++ compiler has some ANSI incompatibility in that it uses _set_new_handler() rather than set_new_handler(). We would naturally conceal this platform difference.
For example:
#include <new> // // New handler for Microsoft Visual C++ compiler // #ifdef _MSC_VER #include <new.h> int __cdecl _newHandler(size_t size ) { // Do whatever return 0; } #else // // Ansi C/C++ new handler // void __cdecl _newHandler( void ) { // Do whatever } #endif void sethandlers(void) { // Microsoft compiler #ifdef _MSC_VER _set_new_handler (_newHandler); // Setup new handler _set_new_mode( 1 ); // Re-route malloc failures to new handler ! // Ansi compiler #else set_new_handler (_newHandler); // ANSI new handler #endif }
The above suggested solution could work for some compilers, but may not for all (some compilers might not support setting a malloc failure callback.) Therefore a Tcl custom new handler functionality could be implemented that handles Tcl specific memory allocation failures.
Something like: Tcl_SetMemHandler()?
This document has been placed in the public domain.
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