SUPPORT_DIRECT_MALLOC and SUPPORT_REMOVE_MALLOC_LEGACY
This supports three build modes: No additional -D options, default legacy mode -DSUPPORT_DIRECT_MALLOC, magic will use direct calls to libc malloc/free and will leave in place the symbols now renamed as mallocMagicLegacy() freeMagicLegacy() and callocMagicLegacy(). -DSUPPORT_DIRECT_MALLOC -DSUPPORT_REMOVE_MALLOC_LEGACY as above but will remove the three legacy functions from the binary to provide assurance they can not be used. The system malloc is thread-safe the legacy magic malloc has a global deferred free pointer and the mmap() allocate has a free-list that is not thread-safe making use of free not thread-safe. This could of course be improved with the use of atomic_compare_and_exchange operations but for what gain ? Then there is the additional function call overhead (of the indirection) and a few tests/branches inserted into a commonly used code paths around memory allocation, it hides the call site of the malloc/free usage from the compiler which maybe have special optimization cases. The existing malloc/free makes static code analysis around memory allocation more problematic, also use of runtime analysers will operate better with a fail-fast to bad memory usage.
This commit is contained in:
Darryl L. Miles
R. Timothy Edwards
parent
97134848ab
commit
ef419258ab
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@ -133,9 +133,11 @@ extern char *SysLibPath; /* Path for finding system
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* Just for the sake of robustness, though, we define malloc and free
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* here to error strings.
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*/
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#ifndef SUPPORT_DIRECT_MALLOC
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#define malloc You_should_use_the_Magic_procedure_mallocMagic_instead
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#define free You_should_use_the_Magic_procedure_freeMagic_instead
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#define calloc You_should_use_the_Magic_procedure_callocMagic_instead
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#endif
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/* ---------- Flag for global variables (for readability) ------------- */
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@ -43,14 +43,18 @@ static char rcsid[] __attribute__ ((unused)) = "$Header: /usr/cvsroot/magic-8.0/
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#include <string.h>
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#include "tcltk/tclmagic.h"
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#define _MAGIC__UTILS__MALLOC_H__NOINLINE
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#include "utils/magic.h"
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#include "utils/malloc.h"
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/* Normally we're supposed to warn against the use of standard malloc() */
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/* and free(), but obviously that doesn't apply to this file. */
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#ifndef SUPPORT_DIRECT_MALLOC
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/* this is needed to remove the utils/magic.h defines */
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#undef malloc
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#undef free
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#endif
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/* Imports */
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@ -64,6 +68,7 @@ extern char *TxGetLine();
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* would no further references would be made to free'ed storage.
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*/
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#ifndef SUPPORT_REMOVE_MALLOC_LEGACY
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/* Delay free'ing by one call, to accommodate Magic's needs. */
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static char *freeDelayedItem = NULL;
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@ -92,14 +97,14 @@ static char *freeDelayedItem = NULL;
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/*
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*---------------------------------------------------------------------
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* mallocMagic() --
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* mallocMagicLegacy() --
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*
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* memory allocator with support for one-delayed-item free'ing
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*---------------------------------------------------------------------
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*/
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void *
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mallocMagic(nbytes)
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mallocMagicLegacy(nbytes)
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size_t nbytes;
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{
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void *p;
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@ -127,14 +132,14 @@ mallocMagic(nbytes)
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/*
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*---------------------------------------------------------------------
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* freeMagic() --
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* freeMagicLegacy() --
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*
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* one-delayed-item memory deallocation
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*---------------------------------------------------------------------
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*/
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void
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freeMagic(cp)
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freeMagicLegacy(cp)
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void *cp;
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{
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if (cp == NULL)
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@ -150,14 +155,14 @@ freeMagic(cp)
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/*
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*---------------------------------------------------------------------
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* callocMagic() --
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* callocMagicLegacy() --
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*
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* allocate memory and initialize it to all zero bytes.
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*---------------------------------------------------------------------
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*/
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void *
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callocMagic(nbytes)
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callocMagicLegacy(nbytes)
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size_t nbytes;
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{
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void *cp;
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@ -168,3 +173,42 @@ callocMagic(nbytes)
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return (cp);
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}
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#endif /* SUPPORT_REMOVE_MALLOC_LEGACY */
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/*
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* NOTICE: non-inline form of emitted functions, keep in sync with malloc.h
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*/
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#pragma weak freeMagic1_init = freeMagic1_init_func
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free_magic1_t freeMagic1_init_func() {
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return NULL;
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}
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#pragma weak freeMagic1 = freeMagic1_func
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void freeMagic1_func(free_magic1_t* m1, void* ptr) {
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//if(*m1) /* this if() is here to help inliner remove the call to free() when it can */
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/* this is not the inline form here so if() is commented out */
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{
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#if (defined(SUPPORT_DIRECT_MALLOC) || defined(SUPPORT_REMOVE_MALLOC_LEGACY))
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free(*m1); /* no need for NULL check with free() */
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#else
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/* but freeMagicLegacy() does not like NULL passed, so extra if() penalty here */
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if(*m1) freeMagicLegacy(*m1);
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#endif
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}
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*m1 = ptr;
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}
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#pragma weak freeMagic1_end = freeMagic1_end_func
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void freeMagic1_end_func(free_magic1_t* m1) {
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//if(*m1) /* this if() is here to help inliner remove the call to free() when it can */
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/* this is not the inline form here so if() is commented out */
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{
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#if (defined(SUPPORT_DIRECT_MALLOC) || defined(SUPPORT_REMOVE_MALLOC_LEGACY))
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free(*m1); /* no need for NULL check with free() */
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#else
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/* but freeMagicLegacy() does not like NULL passed, so extra if() penalty here */
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if(*m1) freeMagicLegacy(*m1);
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#endif
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}
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}
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@ -22,8 +22,95 @@
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#ifndef _MAGIC__UTILS__MALLOC_H
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#define _MAGIC__UTILS__MALLOC_H
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extern void *mallocMagic(size_t);
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extern void *callocMagic(size_t);
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extern void freeMagic(void *);
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#include <stdlib.h>
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/* build time configuration check */
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#if (!defined(SUPPORT_DIRECT_MALLOC) && defined(SUPPORT_REMOVE_MALLOC_LEGACY))
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#error "ERROR: Unspported build configuration SUPPORT_REMOVE_MALLOC_LEGACY is defined but SUPPORT_DIRECT_MALLOC is undefined"
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#endif
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#ifdef SUPPORT_DIRECT_MALLOC
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#define mallocMagic malloc
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#define callocMagic calloc
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#define freeMagic free
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#else
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extern void *mallocMagicLegacy(size_t);
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#define mallocMagic(size) mallocMagicLegacy(size)
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/* renamed like this, so there is no performance loss if the byte count
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* can be computed at compile time.
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*/
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extern void *callocMagicLegacy(size_t);
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#define callocMagic(nmemb, size) callocMagicLegacy((nmemb) * (size))
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extern void freeMagicLegacy(void *);
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#define freeMagic(ptr) freeMagicLegacy(ptr)
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#endif /* SUPPORT_DIRECT_MALLOC */
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typedef void* free_magic1_t;
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/* TODO this should be moved to autoconf/build/toolchain detection, this does exist
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* in autoconf and in another changeset, so I come back and fixup/remove this later.
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*/
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#if (defined(__STDC__) && defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L))
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/* C99 or later */
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#ifndef __inline__
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/* you'd have thought on linux this was enabled already, TODO check bplane module inlines */
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#define __inline__ inline
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#endif
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#endif
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#if (!defined(_MAGIC__UTILS__MALLOC_H__NOINLINE) && defined(__inline__))
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/* TODO this (__extern_inline__) should be moved to autoconf/build/toolchain detection */
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#define __extern_inline__ inline
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/*
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* NOTICE: inline form, keep in sync with malloc.c copied
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*/
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__extern_inline__ free_magic1_t freeMagic1_init() {
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return NULL;
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}
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__extern_inline__ void freeMagic1(free_magic1_t* m1, void* ptr) {
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if(*m1) /* this if() is here to help inliner remove the call to free() when it can */
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{
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#if (defined(SUPPORT_DIRECT_MALLOC) || defined(SUPPORT_REMOVE_MALLOC_LEGACY))
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free(*m1); /* no need for NULL check with free() */
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#else
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freeMagicLegacy(*m1);
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#endif
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}
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*m1 = ptr;
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}
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__extern_inline__ void freeMagic1_end(free_magic1_t* m1) {
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if(*m1) /* this if() is here to help inliner remove the call to free() when it can */
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{
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#if (defined(SUPPORT_DIRECT_MALLOC) || defined(SUPPORT_REMOVE_MALLOC_LEGACY))
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free(*m1); /* no need for NULL check with free() */
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#else
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freeMagicLegacy(*m1);
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#endif
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}
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}
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#else
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#define freeMagic1_init() freeMagic1_init_func()
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#define freeMagic1(m1, ptr) freeMagic1_func((m1), (ptr))
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#define freeMagic1_end(m1) freeMagic1_end_func((m1))
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#endif /* !_MAGIC__UTILS__MALLOC_H__NOINLINE && __inline__ */
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/* we'll emit a function call interface just in case a platform won't inline and we can redirect */
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extern free_magic1_t freeMagic1_init_func(void);
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extern void freeMagic1_func(free_magic1_t* m1, void* ptr);
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extern void freeMagic1_end_func(free_magic1_t* m1);
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#endif /* _MAGIC__UTILS__MALLOC_H */
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