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Memory manangement routines for exception objects
llvm-svn: 135587
This commit is contained in:
Marshall Clow
parent
1df50ca6a2
commit
e2dcb75b2e
107
libcxxabi/src/cxa_exception.cpp
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107
libcxxabi/src/cxa_exception.cpp
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@ -0,0 +1,107 @@
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//===------------------------- cxa_exception.cpp --------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//
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// This file implements the "Exception Handling APIs"
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// http://www.codesourcery.com/public/cxx-abi/abi-eh.html
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//
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//===----------------------------------------------------------------------===//
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#include "cxxabi.h"
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#include <exception> // for std::terminate
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#include <cstdlib> // for malloc, free
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#include <string> // for memset
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#include <pthread.h>
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#include "cxa_exception.hpp"
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#include "cxa_exception_storage.hpp"
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namespace __cxxabiv1 {
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// Utility routines
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static __cxa_exception *exception_from_object ( void *p ) {
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return ((__cxa_exception *) p ) - 1;
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}
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void * object_from_exception ( void *p ) {
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return (void *) (((__cxa_exception *) p ) + 1 );
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}
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static size_t object_size_from_exception_size ( size_t size ) {
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return size + sizeof (__cxa_exception);
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}
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#include "fallback_malloc.cpp"
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// Allocate some memory from _somewhere_
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static void *do_malloc ( size_t size ) throw () {
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void *ptr = std::malloc ( size );
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if ( NULL == ptr ) // if malloc fails, fall back to emergency stash
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ptr = fallback_malloc ( size );
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return ptr;
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}
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// Didn't know you could "return <expression>" from a void function, did you?
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// Well, you can, if the type of the expression is "void" also.
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static void do_free ( void *ptr ) throw () {
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return is_fallback_ptr ( ptr ) ? fallback_free ( ptr ) : std::free ( ptr );
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}
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static thread_local_storage<__cxa_eh_globals> __globals;
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// pthread_once_t __globals::flag_ = PTHREAD_ONCE_INIT;
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extern "C" {
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// Allocate a __cxa_exception object, and zero-fill it.
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// Reserve "thrown_size" bytes on the end for the user's exception
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// object. Zero-fill the object. If memory can't be allocated, call
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// std::terminate. Return a pointer to the memory to be used for the
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// user's exception object.
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void * __cxa_allocate_exception (size_t thrown_size) throw() {
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size_t actual_size = object_size_from_exception_size ( thrown_size );
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void *ptr = do_malloc ( actual_size );
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if ( NULL == ptr )
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std::terminate ();
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std::memset ( ptr, 0, actual_size );
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return object_from_exception ( ptr );
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}
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// Free a __cxa_exception object allocated with __cxa_allocate_exception.
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void __cxa_free_exception (void * thrown_exception) throw() {
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do_free ( exception_from_object ( thrown_exception ));
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}
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// This function shall allocate a __cxa_dependent_exception and
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// return a pointer to it. (Really to the object, not past its' end).
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// Otherwise, it will work like __cxa_allocate_exception.
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void * __cxa_allocate_dependent_exception () throw() {
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size_t actual_size = sizeof ( __cxa_dependent_exception );
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void *ptr = do_malloc ( actual_size );
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if ( NULL == ptr )
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std::terminate ();
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std::memset ( ptr, 0, actual_size );
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// bookkeeping here ?
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return ptr;
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}
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// This function shall free a dependent_exception.
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// It does not affect the reference count of the primary exception.
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void __cxa_free_dependent_exception (void * dependent_exception) throw() {
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// I'm pretty sure there's no bookkeeping here
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do_free ( dependent_exception );
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}
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__cxa_eh_globals * __cxa_get_globals () throw() { return __globals.get_tls (); }
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__cxa_eh_globals * __cxa_get_globals_fast () throw() { return __globals.get_tls_fast (); }
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} // extern "C"
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} // abi
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161
libcxxabi/src/fallback_malloc.cpp
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161
libcxxabi/src/fallback_malloc.cpp
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// A small, simple heap manager based (loosely) on the startup heap
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// based on the startup heap manager from FreeBSD.
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//
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// Manages a fixed-size memory pool, supports malloc and free only.
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// No support for realloc.
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//
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// Allocates chunks in multiples of four bytes, with a four byte header
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// for each chunk. The overhead of each chunk is kept low by keeping pointers
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// as two byte offsets within the heap, rather than (4 or 8 byte) pointers.
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namespace {
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static pthread_mutex_t heap_mutex = PTHREAD_MUTEX_INITIALIZER;
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class mutexor {
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public:
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mutexor ( pthread_mutex_t *m ) : mtx_(m) { pthread_mutex_lock ( mtx_ ); }
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~mutexor () { pthread_mutex_unlock ( mtx_ ); }
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private:
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mutexor ( const mutexor &rhs );
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mutexor & operator = ( const mutexor &rhs );
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pthread_mutex_t *mtx_;
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};
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#define HEAP_SIZE 512
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char heap [ HEAP_SIZE ];
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typedef unsigned short heap_offset;
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typedef unsigned short heap_size;
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struct heap_node {
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heap_offset next_node; // offset into heap
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heap_size len; // size in units of "sizeof(heap_node)"
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};
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static const heap_node *list_end = (heap_node *) ( &heap [ HEAP_SIZE ] ); // one past the end of the heap
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static heap_node *freelist = NULL;
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heap_node *node_from_offset ( const heap_offset offset ) throw()
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{ return (heap_node *) ( heap + ( offset * sizeof (heap_node))); }
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heap_offset offset_from_node ( const heap_node *ptr ) throw()
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{ return (((char *) ptr ) - heap) / sizeof (heap_node); }
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void init_heap () throw() {
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freelist = (heap_node *) heap;
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freelist->next_node = offset_from_node ( list_end );
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freelist->len = HEAP_SIZE / sizeof (heap_node);
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}
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// How big a chunk we allocate
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size_t alloc_size (size_t len) throw()
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{ return (len + sizeof(heap_node) - 1) / sizeof(heap_node) + 1; }
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bool is_fallback_ptr ( void *ptr ) throw()
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{ return ptr >= heap && ptr < ( heap + HEAP_SIZE ); }
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void *fallback_malloc(size_t len) throw() {
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heap_node *p, *prev;
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const size_t nelems = alloc_size ( len );
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mutexor mtx ( &heap_mutex );
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if ( NULL == freelist )
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init_heap ();
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// Walk the free list, looking for a "big enough" chunk
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for (p = freelist, prev = 0;
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p && p != list_end; prev = p, p = node_from_offset ( p->next_node)) {
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if (p->len > nelems) { // chunk is larger, shorten, and return the tail
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heap_node *q;
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p->len -= nelems;
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q = p + p->len;
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q->next_node = 0;
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q->len = nelems;
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return (void *) (q + 1);
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}
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if (p->len == nelems) { // exact size match
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if (prev == 0)
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freelist = node_from_offset(p->next_node);
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else
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prev->next_node = p->next_node;
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p->next_node = 0;
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return (void *) (p + 1);
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}
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}
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return NULL; // couldn't find a spot big enough
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}
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// Return the start of the next block
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heap_node *after ( struct heap_node *p ) throw() { return p + p->len; }
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void fallback_free (void *ptr) throw() {
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struct heap_node *cp = ((struct heap_node *) ptr) - 1; // retrieve the chunk
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struct heap_node *p, *prev;
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mutexor mtx ( &heap_mutex );
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#ifdef DEBUG_FALLBACK_MALLOC
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std::cout << "Freeing item at " << offset_from_node ( cp ) << " of size " << cp->len << std::endl;
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#endif
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for (p = freelist, prev = 0;
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p && p != list_end; prev = p, p = node_from_offset (p->next_node)) {
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#ifdef DEBUG_FALLBACK_MALLOC
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std::cout << " p, cp, after (p), after(cp) "
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<< offset_from_node ( p ) << ' '
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<< offset_from_node ( cp ) << ' '
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<< offset_from_node ( after ( p )) << ' '
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<< offset_from_node ( after ( cp )) << std::endl;
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#endif
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if ( after ( p ) == cp ) {
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#ifdef DEBUG_FALLBACK_MALLOC
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std::cout << " Appending onto chunk at " << offset_from_node ( p ) << std::endl;
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#endif
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p->len += cp->len; // make the free heap_node larger
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return;
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}
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else if ( after ( cp ) == p ) { // there's a free heap_node right after
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#ifdef DEBUG_FALLBACK_MALLOC
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std::cout << " Appending free chunk at " << offset_from_node ( p ) << std::endl;
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#endif
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cp->len += p->len;
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if ( prev == 0 ) {
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freelist = cp;
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cp->next_node = p->next_node;
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}
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else
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prev->next_node = offset_from_node(cp);
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return;
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}
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}
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// Nothing to merge with, add it to the start of the free list
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#ifdef DEBUG_FALLBACK_MALLOC
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std::cout << " Making new free list entry " << offset_from_node ( cp ) << std::endl;
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#endif
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cp->next_node = offset_from_node ( freelist );
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freelist = cp;
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}
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#ifdef INSTRUMENT_FALLBACK_MALLOC
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size_t print_free_list () {
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struct heap_node *p, *prev;
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heap_size total_free = 0;
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if ( NULL == freelist )
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init_heap ();
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for (p = freelist, prev = 0;
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p && p != list_end; prev = p, p = node_from_offset (p->next_node)) {
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std::cout << ( prev == 0 ? "" : " ") << "Offset: " << offset_from_node ( p )
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<< "\tsize: " << p->len << " Next: " << p->next_node << std::endl;
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total_free += p->len;
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}
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std::cout << "Total Free space: " << total_free << std::endl;
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return total_free;
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}
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#endif
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}
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180
libcxxabi/test/test_fallback_malloc.cpp
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180
libcxxabi/test/test_fallback_malloc.cpp
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@ -0,0 +1,180 @@
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#include <iostream>
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#include <deque>
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#include <pthread.h>
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typedef std::deque<void *> container;
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// #define DEBUG_FALLBACK_MALLOC
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#define INSTRUMENT_FALLBACK_MALLOC
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#include "../src/fallback_malloc.cpp"
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container alloc_series ( size_t sz ) {
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container ptrs;
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void *p;
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while ( NULL != ( p = fallback_malloc ( sz )))
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ptrs.push_back ( p );
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return ptrs;
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}
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container alloc_series ( size_t sz, float growth ) {
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container ptrs;
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void *p;
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while ( NULL != ( p = fallback_malloc ( sz ))) {
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ptrs.push_back ( p );
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sz *= growth;
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}
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return ptrs;
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}
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container alloc_series ( const size_t *first, size_t len ) {
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container ptrs;
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const size_t *last = first + len;
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void * p;
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for ( const size_t *iter = first; iter != last; ++iter ) {
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if ( NULL == (p = fallback_malloc ( *iter )))
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break;
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ptrs.push_back ( p );
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}
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return ptrs;
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}
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void *pop ( container &c, bool from_end ) {
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void *ptr;
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if ( from_end ) {
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ptr = c.back ();
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c.pop_back ();
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}
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else {
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ptr = c.front ();
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c.pop_front ();
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}
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return ptr;
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}
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void exhaustion_test1 () {
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container ptrs;
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init_heap ();
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std::cout << "Constant exhaustion tests" << std::endl;
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// Delete in allocation order
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ptrs = alloc_series ( 32 );
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std::cout << "Allocated " << ptrs.size () << " 32 byte chunks" << std::endl;
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print_free_list ();
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for ( container::iterator iter = ptrs.begin (); iter != ptrs.end (); ++iter )
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fallback_free ( *iter );
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print_free_list ();
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std::cout << "----" << std::endl;
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// Delete in reverse order
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ptrs = alloc_series ( 32 );
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std::cout << "Allocated " << ptrs.size () << " 32 byte chunks" << std::endl;
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for ( container::reverse_iterator iter = ptrs.rbegin (); iter != ptrs.rend (); ++iter )
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fallback_free ( *iter );
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print_free_list ();
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std::cout << "----" << std::endl;
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// Alternate deletions
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ptrs = alloc_series ( 32 );
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std::cout << "Allocated " << ptrs.size () << " 32 byte chunks" << std::endl;
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while ( ptrs.size () > 0 )
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fallback_free ( pop ( ptrs, ptrs.size () % 1 == 1 ));
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print_free_list ();
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}
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void exhaustion_test2 () {
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container ptrs;
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init_heap ();
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std::cout << "Growing exhaustion tests" << std::endl;
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// Delete in allocation order
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ptrs = alloc_series ( 32, 1.5 );
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std::cout << "Allocated " << ptrs.size () << " { 32, 48, 72, 108, 162 ... } byte chunks" << std::endl;
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print_free_list ();
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for ( container::iterator iter = ptrs.begin (); iter != ptrs.end (); ++iter )
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fallback_free ( *iter );
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print_free_list ();
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std::cout << "----" << std::endl;
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// Delete in reverse order
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print_free_list ();
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ptrs = alloc_series ( 32, 1.5 );
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std::cout << "Allocated " << ptrs.size () << " { 32, 48, 72, 108, 162 ... } byte chunks" << std::endl;
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for ( container::reverse_iterator iter = ptrs.rbegin (); iter != ptrs.rend (); ++iter )
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fallback_free ( *iter );
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print_free_list ();
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std::cout << "----" << std::endl;
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// Alternate deletions
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ptrs = alloc_series ( 32, 1.5 );
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std::cout << "Allocated " << ptrs.size () << " { 32, 48, 72, 108, 162 ... } byte chunks" << std::endl;
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while ( ptrs.size () > 0 )
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fallback_free ( pop ( ptrs, ptrs.size () % 1 == 1 ));
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print_free_list ();
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}
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void exhaustion_test3 () {
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const size_t allocs [] = { 124, 60, 252, 60, 4 };
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container ptrs;
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init_heap ();
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std::cout << "Complete exhaustion tests" << std::endl;
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// Delete in allocation order
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ptrs = alloc_series ( allocs, sizeof ( allocs ) / sizeof ( allocs[0] ));
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std::cout << "Allocated " << ptrs.size () << " chunks" << std::endl;
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print_free_list ();
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for ( container::iterator iter = ptrs.begin (); iter != ptrs.end (); ++iter )
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fallback_free ( *iter );
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print_free_list ();
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std::cout << "----" << std::endl;
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// Delete in reverse order
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print_free_list ();
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ptrs = alloc_series ( allocs, sizeof ( allocs ) / sizeof ( allocs[0] ));
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std::cout << "Allocated " << ptrs.size () << " chunks" << std::endl;
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for ( container::reverse_iterator iter = ptrs.rbegin (); iter != ptrs.rend (); ++iter )
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fallback_free ( *iter );
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print_free_list ();
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std::cout << "----" << std::endl;
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// Alternate deletions
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ptrs = alloc_series ( allocs, sizeof ( allocs ) / sizeof ( allocs[0] ));
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std::cout << "Allocated " << ptrs.size () << " chunks" << std::endl;
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while ( ptrs.size () > 0 )
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fallback_free ( pop ( ptrs, ptrs.size () % 1 == 1 ));
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print_free_list ();
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}
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int main ( int argc, char *argv [] ) {
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print_free_list ();
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char *p = (char *) fallback_malloc ( 1024 ); // too big!
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std::cout << "fallback_malloc ( 1024 ) --> " << (unsigned long ) p << std::endl;
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print_free_list ();
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p = (char *) fallback_malloc ( 32 );
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std::cout << "fallback_malloc ( 32 ) --> " << (unsigned long) (p - heap) << std::endl;
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if ( !is_fallback_ptr ( p ))
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std::cout << "### p is not a fallback pointer!!" << std::endl;
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print_free_list ();
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fallback_free ( p );
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print_free_list ();
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std::cout << std::endl;
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exhaustion_test1 (); std::cout << std::endl;
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exhaustion_test2 (); std::cout << std::endl;
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exhaustion_test3 (); std::cout << std::endl;
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return 0;
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}
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