1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)malloc.3 8.1 (Berkeley) 6/4/93
| 1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)malloc.3 8.1 (Berkeley) 6/4/93
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38.\" 39.Dd August 27, 1996 40.Dt MALLOC 3 41.Os 42.Sh NAME 43.Nm malloc , calloc , realloc , free , reallocf 44.Nd general purpose memory allocation functions 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.Fd #include <stdlib.h> 49.Ft void * 50.Fn malloc "size_t size" 51.Ft void * 52.Fn calloc "size_t number" "size_t size" 53.Ft void * 54.Fn realloc "void *ptr" "size_t size" 55.Ft void * 56.Fn reallocf "void *ptr" "size_t size" 57.Ft void 58.Fn free "void *ptr" 59.Ft char * 60.Va _malloc_options 61.Ft void 62.Fn \*(lp*_malloc_message\*(rp "char *p1" "char *p2" "char *p3" "char *p4" 63.Sh DESCRIPTION 64The 65.Fn malloc 66function allocates 67.Fa size 68bytes of memory. 69The allocated space is suitably aligned (after possible pointer coercion) 70for storage of any type of object. 71If the space is at least 72.Em pagesize 73bytes in length (see 74.Xr getpagesize 3 ) , 75the returned memory will be page boundary aligned as well. 76If 77.Fn malloc 78fails, a 79.Dv NULL 80pointer is returned. 81.Pp 82Note that 83.Fn malloc 84does 85.Em NOT 86normally initialize the returned memory to zero bytes. 87.Pp 88The 89.Fn calloc 90function allocates space for 91.Fa number 92objects, 93each 94.Fa size 95bytes in length. 96The result is identical to calling 97.Fn malloc 98with an argument of 99.Dq "number * size" , 100with the exception that the allocated memory is explicitly initialized 101to zero bytes. 102.Pp 103The 104.Fn realloc 105function changes the size of the previously allocated memory referenced by 106.Fa ptr 107to 108.Fa size 109bytes. 110The contents of the memory are unchanged up to the lesser of the new and 111old sizes. 112If the new size is larger, 113the value of the newly allocated portion of the memory is undefined. 114If the requested memory cannot be allocated, 115.Dv NULL 116is returned and 117the memory referenced by 118.Fa ptr 119is valid and unchanged. 120If 121.Fa ptr 122is 123.Dv NULL , 124the 125.Fn realloc 126function behaves identically to 127.Fn malloc 128for the specified size. 129.Pp 130The 131.Fn reallocf 132function call is identical to the realloc function call, except that it 133will free the passed pointer when the requested memory cannot be allocated. 134This is a 135.Fx 136specific API designed to ease the problems with traditional coding styles 137for realloc causing memory leaks in libraries. 138.Pp 139The 140.Fn free 141function causes the allocated memory referenced by 142.Fa ptr 143to be made available for future allocations. 144If 145.Fa ptr 146is 147.Dv NULL , 148no action occurs. 149.Sh TUNING 150Once, when the first call is made to one of these memory allocation 151routines, various flags will be set or reset, which affect the 152workings of this allocation implementation. 153.Pp 154The ``name'' of the file referenced by the symbolic link named 155.Pa /etc/malloc.conf , 156the value of the environment variable 157.Ev MALLOC_OPTIONS , 158and the string pointed to by the global variable 159.Va _malloc_options 160will be interpreted, in that order, character by character as flags. 161.Pp 162Most flags are single letters, 163where uppercase indicates that the behavior is set, or on, 164and lowercase means that the behavior is not set, or off. 165.Bl -tag -width indent 166.It A 167All warnings (except for the warning about unknown 168flags being set) become fatal. 169The process will call 170.Xr abort 3 171in these cases. 172.It J 173Each byte of new memory allocated by 174.Fn malloc , 175.Fn realloc 176or 177.Fn reallocf 178as well as all memory returned by 179.Fn free , 180.Fn realloc 181or 182.Fn reallocf 183will be initialized to 0xd0. 184This options also sets the 185.Dq R 186option. 187This is intended for debugging and will impact performance negatively. 188.It H 189Pass a hint to the kernel about pages unused by the allocation functions. 190This will help performance if the system is paging excessively. This 191option is off by default. 192.It R 193Causes the 194.Fn realloc 195and 196.Fn reallocf 197functions to always reallocate memory even if the initial allocation was 198sufficiently large. 199This can substantially aid in compacting memory. 200.It U 201Generate 202.Dq utrace 203entries for 204.Xr ktrace 1 , 205for all operations. 206Consult the source for details on this option. 207.It V 208Attempting to allocate zero bytes will return a 209.Dv NULL 210pointer instead of 211a valid pointer. 212(The default behavior is to make a minimal allocation and return a 213pointer to it.) 214This option is provided for System V compatibility. 215This option is incompatible with the 216.Dq X 217option. 218.It X 219Rather than return failure for any allocation function, 220display a diagnostic message on stderr and cause the program to drop 221core (using 222.Xr abort 3 ) . 223This option should be set at compile time by including the following in 224the source code: 225.Bd -literal -offset indent 226_malloc_options = "X"; 227.Ed 228.It Z 229This option implicitly sets the 230.Dq J 231and 232.Dq R 233options, and then zeros out the bytes that were requested. 234This is intended for debugging and will impact performance negatively. 235.It < 236Reduce the size of the cache by a factor of two. 237The default cache size is 16 pages. 238This option can be specified multiple times. 239.It > 240Double the size of the cache by a factor of two. 241The default cache size is 16 pages. 242This option can be specified multiple times. 243.El 244.Pp 245The 246.Dq J 247and 248.Dq Z 249options are intended for testing and debugging. 250An application which changes its behavior when these options are used 251is flawed. 252.Sh EXAMPLES 253To set a systemwide reduction of cache size, and to dump core whenever 254a problem occurs: 255.Pp 256.Bd -literal -offset indent 257ln -s 'A<' /etc/malloc.conf 258.Ed 259.Pp 260To specify in the source that a program does no return value checking 261on calls to these functions: 262.Bd -literal -offset indent 263_malloc_options = "X"; 264.Ed 265.Sh ENVIRONMENT 266The following environment variables affect the execution of the allocation 267functions: 268.Bl -tag -width MMM 269.It Ev MALLOC_OPTIONS 270If the environment variable 271.Ev MALLOC_OPTIONS 272is set, the characters it contains will be interpreted as flags to the 273allocation functions. 274.El 275.Sh RETURN VALUES 276The 277.Fn malloc 278and 279.Fn calloc 280functions return a pointer to the allocated memory if successful; otherwise 281a 282.Dv NULL 283pointer is returned and 284.Va errno 285is set to 286.Er ENOMEM . 287.Pp 288The 289.Fn realloc 290and 291.Fn reallocf 292functions return a pointer, possibly identical to 293.Fa ptr , 294to the allocated memory 295if successful; otherwise a 296.Dv NULL 297pointer is returned, in which case the 298memory referenced by 299.Fa ptr 300is still available and intact. 301In the case of memory allocation failure, 302.Va errno 303is set to 304.Er ENOMEM . 305.Pp 306The 307.Fn free 308function returns no value. 309.Sh DEBUGGING MALLOC PROBLEMS 310The major difference between this implementation and other allocation 311implementations is that the free pages are not accessed unless allocated, 312and are aggressively returned to the kernel for reuse. 313.Bd -ragged -offset indent 314Most allocation implementations will store a data structure containing a 315linked list in the free chunks of memory, 316used to tie all the free memory together. 317That can be suboptimal, 318as every time the free-list is traversed, 319the otherwise unused, and likely paged out, 320pages are faulted into primary memory. 321On systems which are paging, 322this can result in a factor of five increase in the number of page-faults 323done by a process. 324.Ed 325.Pp 326A side effect of this architecture is that many minor transgressions on 327the interface which would traditionally not be detected are in fact 328detected. As a result, programs that have been running happily for 329years may suddenly start to complain loudly, when linked with this 330allocation implementation. 331.Pp 332The first and most important thing to do is to set the 333.Dq A 334option. 335This option forces a coredump (if possible) at the first sign of trouble, 336rather than the normal policy of trying to continue if at all possible. 337.Pp 338It is probably also a good idea to recompile the program with suitable 339options and symbols for debugger support. 340.Pp 341If the program starts to give unusual results, coredump or generally behave 342differently without emitting any of the messages listed in the next 343section, it is likely because it depends on the storage being filled with 344zero bytes. Try running it with 345.Dq Z 346option set; 347if that improves the situation, this diagnosis has been confirmed. 348If the program still misbehaves, 349the likely problem is accessing memory outside the allocated area, 350more likely after than before the allocated area. 351.Pp 352Alternatively, if the symptoms are not easy to reproduce, setting the 353.Dq J 354option may help provoke the problem. 355.Pp 356In truly difficult cases, the 357.Dq U 358option, if supported by the kernel, can provide a detailed trace of 359all calls made to these functions. 360.Pp 361Unfortunately this implementation does not provide much detail about 362the problems it detects, the performance impact for storing such information 363would be prohibitive. 364There are a number of allocation implementations available on the 'Net 365which focus on detecting and pinpointing problems by trading performance 366for extra sanity checks and detailed diagnostics. 367.Sh DIAGNOSTIC MESSAGES 368If 369.Fn malloc , 370.Fn calloc , 371.Fn realloc 372or 373.Fn free 374detect an error or warning condition, 375a message will be printed to file descriptor STDERR_FILENO. 376Errors will result in the process dumping core. 377If the 378.Dq A 379option is set, all warnings are treated as errors. 380.Pp 381The 382.Va _malloc_message 383variable allows the programmer to override the function which emits 384the text strings forming the errors and warnings if for some reason 385the stderr filedescriptor is not suitable for this. 386Please note that doing anything which tries to allocate memory in 387this function will assure death of the process. 388.Pp 389The following is a brief description of possible error messages and 390their meanings: 391.Pp 392.Bl -tag -width indent 393.It "(ES): mumble mumble mumble 394The allocation functions were compiled with 395.Dq EXTRA_SANITY 396defined, and an error was found during the additional error checking. 397Consult the source code for further information.
| 38.\" 39.Dd August 27, 1996 40.Dt MALLOC 3 41.Os 42.Sh NAME 43.Nm malloc , calloc , realloc , free , reallocf 44.Nd general purpose memory allocation functions 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.Fd #include <stdlib.h> 49.Ft void * 50.Fn malloc "size_t size" 51.Ft void * 52.Fn calloc "size_t number" "size_t size" 53.Ft void * 54.Fn realloc "void *ptr" "size_t size" 55.Ft void * 56.Fn reallocf "void *ptr" "size_t size" 57.Ft void 58.Fn free "void *ptr" 59.Ft char * 60.Va _malloc_options 61.Ft void 62.Fn \*(lp*_malloc_message\*(rp "char *p1" "char *p2" "char *p3" "char *p4" 63.Sh DESCRIPTION 64The 65.Fn malloc 66function allocates 67.Fa size 68bytes of memory. 69The allocated space is suitably aligned (after possible pointer coercion) 70for storage of any type of object. 71If the space is at least 72.Em pagesize 73bytes in length (see 74.Xr getpagesize 3 ) , 75the returned memory will be page boundary aligned as well. 76If 77.Fn malloc 78fails, a 79.Dv NULL 80pointer is returned. 81.Pp 82Note that 83.Fn malloc 84does 85.Em NOT 86normally initialize the returned memory to zero bytes. 87.Pp 88The 89.Fn calloc 90function allocates space for 91.Fa number 92objects, 93each 94.Fa size 95bytes in length. 96The result is identical to calling 97.Fn malloc 98with an argument of 99.Dq "number * size" , 100with the exception that the allocated memory is explicitly initialized 101to zero bytes. 102.Pp 103The 104.Fn realloc 105function changes the size of the previously allocated memory referenced by 106.Fa ptr 107to 108.Fa size 109bytes. 110The contents of the memory are unchanged up to the lesser of the new and 111old sizes. 112If the new size is larger, 113the value of the newly allocated portion of the memory is undefined. 114If the requested memory cannot be allocated, 115.Dv NULL 116is returned and 117the memory referenced by 118.Fa ptr 119is valid and unchanged. 120If 121.Fa ptr 122is 123.Dv NULL , 124the 125.Fn realloc 126function behaves identically to 127.Fn malloc 128for the specified size. 129.Pp 130The 131.Fn reallocf 132function call is identical to the realloc function call, except that it 133will free the passed pointer when the requested memory cannot be allocated. 134This is a 135.Fx 136specific API designed to ease the problems with traditional coding styles 137for realloc causing memory leaks in libraries. 138.Pp 139The 140.Fn free 141function causes the allocated memory referenced by 142.Fa ptr 143to be made available for future allocations. 144If 145.Fa ptr 146is 147.Dv NULL , 148no action occurs. 149.Sh TUNING 150Once, when the first call is made to one of these memory allocation 151routines, various flags will be set or reset, which affect the 152workings of this allocation implementation. 153.Pp 154The ``name'' of the file referenced by the symbolic link named 155.Pa /etc/malloc.conf , 156the value of the environment variable 157.Ev MALLOC_OPTIONS , 158and the string pointed to by the global variable 159.Va _malloc_options 160will be interpreted, in that order, character by character as flags. 161.Pp 162Most flags are single letters, 163where uppercase indicates that the behavior is set, or on, 164and lowercase means that the behavior is not set, or off. 165.Bl -tag -width indent 166.It A 167All warnings (except for the warning about unknown 168flags being set) become fatal. 169The process will call 170.Xr abort 3 171in these cases. 172.It J 173Each byte of new memory allocated by 174.Fn malloc , 175.Fn realloc 176or 177.Fn reallocf 178as well as all memory returned by 179.Fn free , 180.Fn realloc 181or 182.Fn reallocf 183will be initialized to 0xd0. 184This options also sets the 185.Dq R 186option. 187This is intended for debugging and will impact performance negatively. 188.It H 189Pass a hint to the kernel about pages unused by the allocation functions. 190This will help performance if the system is paging excessively. This 191option is off by default. 192.It R 193Causes the 194.Fn realloc 195and 196.Fn reallocf 197functions to always reallocate memory even if the initial allocation was 198sufficiently large. 199This can substantially aid in compacting memory. 200.It U 201Generate 202.Dq utrace 203entries for 204.Xr ktrace 1 , 205for all operations. 206Consult the source for details on this option. 207.It V 208Attempting to allocate zero bytes will return a 209.Dv NULL 210pointer instead of 211a valid pointer. 212(The default behavior is to make a minimal allocation and return a 213pointer to it.) 214This option is provided for System V compatibility. 215This option is incompatible with the 216.Dq X 217option. 218.It X 219Rather than return failure for any allocation function, 220display a diagnostic message on stderr and cause the program to drop 221core (using 222.Xr abort 3 ) . 223This option should be set at compile time by including the following in 224the source code: 225.Bd -literal -offset indent 226_malloc_options = "X"; 227.Ed 228.It Z 229This option implicitly sets the 230.Dq J 231and 232.Dq R 233options, and then zeros out the bytes that were requested. 234This is intended for debugging and will impact performance negatively. 235.It < 236Reduce the size of the cache by a factor of two. 237The default cache size is 16 pages. 238This option can be specified multiple times. 239.It > 240Double the size of the cache by a factor of two. 241The default cache size is 16 pages. 242This option can be specified multiple times. 243.El 244.Pp 245The 246.Dq J 247and 248.Dq Z 249options are intended for testing and debugging. 250An application which changes its behavior when these options are used 251is flawed. 252.Sh EXAMPLES 253To set a systemwide reduction of cache size, and to dump core whenever 254a problem occurs: 255.Pp 256.Bd -literal -offset indent 257ln -s 'A<' /etc/malloc.conf 258.Ed 259.Pp 260To specify in the source that a program does no return value checking 261on calls to these functions: 262.Bd -literal -offset indent 263_malloc_options = "X"; 264.Ed 265.Sh ENVIRONMENT 266The following environment variables affect the execution of the allocation 267functions: 268.Bl -tag -width MMM 269.It Ev MALLOC_OPTIONS 270If the environment variable 271.Ev MALLOC_OPTIONS 272is set, the characters it contains will be interpreted as flags to the 273allocation functions. 274.El 275.Sh RETURN VALUES 276The 277.Fn malloc 278and 279.Fn calloc 280functions return a pointer to the allocated memory if successful; otherwise 281a 282.Dv NULL 283pointer is returned and 284.Va errno 285is set to 286.Er ENOMEM . 287.Pp 288The 289.Fn realloc 290and 291.Fn reallocf 292functions return a pointer, possibly identical to 293.Fa ptr , 294to the allocated memory 295if successful; otherwise a 296.Dv NULL 297pointer is returned, in which case the 298memory referenced by 299.Fa ptr 300is still available and intact. 301In the case of memory allocation failure, 302.Va errno 303is set to 304.Er ENOMEM . 305.Pp 306The 307.Fn free 308function returns no value. 309.Sh DEBUGGING MALLOC PROBLEMS 310The major difference between this implementation and other allocation 311implementations is that the free pages are not accessed unless allocated, 312and are aggressively returned to the kernel for reuse. 313.Bd -ragged -offset indent 314Most allocation implementations will store a data structure containing a 315linked list in the free chunks of memory, 316used to tie all the free memory together. 317That can be suboptimal, 318as every time the free-list is traversed, 319the otherwise unused, and likely paged out, 320pages are faulted into primary memory. 321On systems which are paging, 322this can result in a factor of five increase in the number of page-faults 323done by a process. 324.Ed 325.Pp 326A side effect of this architecture is that many minor transgressions on 327the interface which would traditionally not be detected are in fact 328detected. As a result, programs that have been running happily for 329years may suddenly start to complain loudly, when linked with this 330allocation implementation. 331.Pp 332The first and most important thing to do is to set the 333.Dq A 334option. 335This option forces a coredump (if possible) at the first sign of trouble, 336rather than the normal policy of trying to continue if at all possible. 337.Pp 338It is probably also a good idea to recompile the program with suitable 339options and symbols for debugger support. 340.Pp 341If the program starts to give unusual results, coredump or generally behave 342differently without emitting any of the messages listed in the next 343section, it is likely because it depends on the storage being filled with 344zero bytes. Try running it with 345.Dq Z 346option set; 347if that improves the situation, this diagnosis has been confirmed. 348If the program still misbehaves, 349the likely problem is accessing memory outside the allocated area, 350more likely after than before the allocated area. 351.Pp 352Alternatively, if the symptoms are not easy to reproduce, setting the 353.Dq J 354option may help provoke the problem. 355.Pp 356In truly difficult cases, the 357.Dq U 358option, if supported by the kernel, can provide a detailed trace of 359all calls made to these functions. 360.Pp 361Unfortunately this implementation does not provide much detail about 362the problems it detects, the performance impact for storing such information 363would be prohibitive. 364There are a number of allocation implementations available on the 'Net 365which focus on detecting and pinpointing problems by trading performance 366for extra sanity checks and detailed diagnostics. 367.Sh DIAGNOSTIC MESSAGES 368If 369.Fn malloc , 370.Fn calloc , 371.Fn realloc 372or 373.Fn free 374detect an error or warning condition, 375a message will be printed to file descriptor STDERR_FILENO. 376Errors will result in the process dumping core. 377If the 378.Dq A 379option is set, all warnings are treated as errors. 380.Pp 381The 382.Va _malloc_message 383variable allows the programmer to override the function which emits 384the text strings forming the errors and warnings if for some reason 385the stderr filedescriptor is not suitable for this. 386Please note that doing anything which tries to allocate memory in 387this function will assure death of the process. 388.Pp 389The following is a brief description of possible error messages and 390their meanings: 391.Pp 392.Bl -tag -width indent 393.It "(ES): mumble mumble mumble 394The allocation functions were compiled with 395.Dq EXTRA_SANITY 396defined, and an error was found during the additional error checking. 397Consult the source code for further information.
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399This most likely means that the system is dangerously overloaded or that 400the process' limits are incorrectly specified. 401.It "freelist is destroyed 402The internal free-list has been corrupted. 403.El 404.Pp 405.Bl -tag -width indent 406The following is a brief description of possible warning messages and 407their meanings: 408.Pp 409.It "chunk/page is already free 410The process attempted to 411.Fn free 412memory which had already been freed. 413.It "junk pointer ... 414A pointer specified to one of the allocation functions points outside the 415bounds of the memory of which they are aware. 416.It "malloc() has never been called 417No memory has been allocated, 418yet something is being freed or 419realloc'ed. 420.It "modified (chunk-/page-) pointer 421The pointer passed to 422.Fn free 423or 424.Fn realloc 425has been modified. 426.It "pointer to wrong page 427The pointer that 428.Fn malloc 429or 430.Fn calloc 431is trying to free does not reference a possible page. 432.It "recursive call 433A process has attempted to call an allocation function recursively. 434This is not permitted. In particular, signal handlers should not 435attempt to allocate memory. 436.It "out of memory 437The 438.Dq X 439option was specified and an allocation of memory failed. 440.It "unknown char in MALLOC_OPTIONS 441An unknown option was specified. 442Even with the 443.Dq A 444option set, this warning is still only a warning. 445.El 446.Sh SEE ALSO 447.Xr brk 2 , 448.Xr mmap 2 , 449.Xr alloca 3 , 450.Xr getpagesize 3 , 451.Xr memory 3 452.Pa /usr/share/doc/papers/malloc.ascii.gz 453.Sh STANDARDS 454The 455.Fn malloc , 456.Fn calloc , 457.Fn realloc 458and 459.Fn free 460functions conform to 461.St -isoC . 462.Sh HISTORY 463The present allocation implementation started out as a filesystem for a 464drum attached to a 20bit binary challenged computer which was built 465with discrete germanium transistors. It has since graduated to 466handle primary storage rather than secondary. 467It first appeared in its new shape and ability in 468.Fx 2.2 . 469.Pp 470The 471.Xr reallocf 3 472function first appeared in 473.Fx 3.0 . 474.Sh AUTHORS 475.An Poul-Henning Kamp Aq phk@FreeBSD.org 476.Sh BUGS 477The messages printed in case of problems provide no detail about the 478actual values. 479.Pp 480It can be argued that returning a 481.Dv NULL 482pointer when asked to 483allocate zero bytes is a silly response to a silly question.
| 402This most likely means that the system is dangerously overloaded or that 403the process' limits are incorrectly specified. 404.It "freelist is destroyed 405The internal free-list has been corrupted. 406.El 407.Pp 408.Bl -tag -width indent 409The following is a brief description of possible warning messages and 410their meanings: 411.Pp 412.It "chunk/page is already free 413The process attempted to 414.Fn free 415memory which had already been freed. 416.It "junk pointer ... 417A pointer specified to one of the allocation functions points outside the 418bounds of the memory of which they are aware. 419.It "malloc() has never been called 420No memory has been allocated, 421yet something is being freed or 422realloc'ed. 423.It "modified (chunk-/page-) pointer 424The pointer passed to 425.Fn free 426or 427.Fn realloc 428has been modified. 429.It "pointer to wrong page 430The pointer that 431.Fn malloc 432or 433.Fn calloc 434is trying to free does not reference a possible page. 435.It "recursive call 436A process has attempted to call an allocation function recursively. 437This is not permitted. In particular, signal handlers should not 438attempt to allocate memory. 439.It "out of memory 440The 441.Dq X 442option was specified and an allocation of memory failed. 443.It "unknown char in MALLOC_OPTIONS 444An unknown option was specified. 445Even with the 446.Dq A 447option set, this warning is still only a warning. 448.El 449.Sh SEE ALSO 450.Xr brk 2 , 451.Xr mmap 2 , 452.Xr alloca 3 , 453.Xr getpagesize 3 , 454.Xr memory 3 455.Pa /usr/share/doc/papers/malloc.ascii.gz 456.Sh STANDARDS 457The 458.Fn malloc , 459.Fn calloc , 460.Fn realloc 461and 462.Fn free 463functions conform to 464.St -isoC . 465.Sh HISTORY 466The present allocation implementation started out as a filesystem for a 467drum attached to a 20bit binary challenged computer which was built 468with discrete germanium transistors. It has since graduated to 469handle primary storage rather than secondary. 470It first appeared in its new shape and ability in 471.Fx 2.2 . 472.Pp 473The 474.Xr reallocf 3 475function first appeared in 476.Fx 3.0 . 477.Sh AUTHORS 478.An Poul-Henning Kamp Aq phk@FreeBSD.org 479.Sh BUGS 480The messages printed in case of problems provide no detail about the 481actual values. 482.Pp 483It can be argued that returning a 484.Dv NULL 485pointer when asked to 486allocate zero bytes is a silly response to a silly question.
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