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1 | '\" |
2 | '\" Copyright (c) 1992-1999 Karl Lehenbauer and Mark Diekhans. | |
3 | '\" Copyright (c) 2000 by Scriptics Corporation. | |
4 | '\" All rights reserved. | |
5 | '\" | |
6 | '\" RCS: @(#) $Id: TCL_MEM_DEBUG.3,v 1.6 2002/11/15 15:34:17 dkf Exp $ | |
7 | '\" | |
8 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
9 | '\" manual entries. | |
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11 | '\" .AP type name in/out ?indent? | |
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36 | '\" .VS ?version? ?br? | |
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69 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ | |
70 | '\" | |
71 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. | |
72 | .if t .wh -1.3i ^B | |
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175 | .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c | |
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204 | '\" # SO - start of list of standard options | |
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206 | .SH "STANDARD OPTIONS" | |
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209 | .ta 5.5c 11c | |
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212 | '\" # SE - end of list of standard options | |
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217 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
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224 | Command-Line Name: \\fB\\$1\\fR | |
225 | Database Name: \\fB\\$2\\fR | |
226 | Database Class: \\fB\\$3\\fR | |
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242 | \\$1\l'|0\(ul'\\$2 | |
243 | .. | |
244 | .TH TCL_MEM_DEBUG 3 8.1 Tcl "Tcl Library Procedures" | |
245 | .BS | |
246 | .SH NAME | |
247 | TCL_MEM_DEBUG \- Compile-time flag to enable Tcl memory debugging. | |
248 | .BE | |
249 | ||
250 | .SH DESCRIPTION | |
251 | When Tcl is compiled with \fBTCL_MEM_DEBUG\fR defined, a powerful set | |
252 | of memory debugging aids are included in the compiled binary. This | |
253 | includes C and Tcl functions which can aid with debugging | |
254 | memory leaks, memory allocation overruns, and other memory related | |
255 | errors. | |
256 | ||
257 | .SH "ENABLING MEMORY DEBUGGING" | |
258 | .PP | |
259 | To enable memory debugging, Tcl should be recompiled from scratch with | |
260 | \fBTCL_MEM_DEBUG\fR defined. This will also compile in a non-stub | |
261 | version of \fBTcl_InitMemory\fR to add the \fBmemory\fR command to Tcl. | |
262 | .PP | |
263 | \fBTCL_MEM_DEBUG\fR must be either left defined for all modules or undefined | |
264 | for all modules that are going to be linked together. If they are not, link | |
265 | errors will occur, with either \fBTclDbCkfree\fR and \fBTcl_DbCkalloc\fR or | |
266 | \fBTcl_Ckalloc\fR and \fBTcl_Ckfree\fR being undefined. | |
267 | .PP | |
268 | Once memory debugging support has been compiled into Tcl, the C | |
269 | functions \fBTcl_ValidateAllMemory\fR, and \fBTcl_DumpActiveMemory\fR, | |
270 | and the Tcl \fBmemory\fR command can be used to validate and examine | |
271 | memory usage. | |
272 | ||
273 | .SH "GUARD ZONES" | |
274 | .PP | |
275 | When memory debugging is enabled, whenever a call to \fBckalloc\fR is | |
276 | made, slightly more memory than requested is allocated so the memory debugging | |
277 | code can keep track of the allocated memory, and eight-byte ``guard | |
278 | zones'' are placed in front of and behind the space that will be | |
279 | returned to the caller. (The sizes of the guard zones are defined by the | |
280 | C #define \fBLOW_GUARD_SIZE\fR and #define \fBHIGH_GUARD_SIZE\fR | |
281 | in the file \fIgeneric/tclCkalloc.c\fR -- it can | |
282 | be extended if you suspect large overwrite problems, at some cost in | |
283 | performance.) A known pattern is written into the guard zones and, on | |
284 | a call to \fBckfree\fR, the guard zones of the space being freed are | |
285 | checked to see if either zone has been modified in any way. If one | |
286 | has been, the guard bytes and their new contents are identified, and a | |
287 | ``low guard failed'' or ``high guard failed'' message is issued. The | |
288 | ``guard failed'' message includes the address of the memory packet and | |
289 | the file name and line number of the code that called \fBckfree\fR. | |
290 | This allows you to detect the common sorts of one-off problems, where | |
291 | not enough space was allocated to contain the data written, for | |
292 | example. | |
293 | ||
294 | .SH "DEBUGGING DIFFICULT MEMORY CORRUPTION PROBLEMS" | |
295 | .PP | |
296 | Normally, Tcl compiled with memory debugging enabled will make it easy | |
297 | to isolate a corruption problem. Turning on memory validation with | |
298 | the memory command can help isolate difficult problems. If you | |
299 | suspect (or know) that corruption is occurring before the Tcl | |
300 | interpreter comes up far enough for you to issue commands, you can set | |
301 | \fBMEM_VALIDATE\fR define, recompile tclCkalloc.c and rebuild Tcl. | |
302 | This will enable memory validation from the first call to | |
303 | \fBckalloc\fR, again, at a large performance impact. | |
304 | .PP | |
305 | If you are desperate and validating memory on every call to | |
306 | \fBckalloc\fR and \fBckfree\fR isn't enough, you can explicitly call | |
307 | \fBTcl_ValidateAllMemory\fR directly at any point. It takes a \fIchar | |
308 | *\fR and an \fIint\fR which are normally the filename and line number | |
309 | of the caller, but they can actually be anything you want. Remember | |
310 | to remove the calls after you find the problem. | |
311 | ||
312 | .SH "SEE ALSO" | |
313 | ckalloc, memory, Tcl_ValidateAllMemory, Tcl_DumpActiveMemory | |
314 | ||
315 | .SH KEYWORDS | |
316 | memory, debug | |
317 | ||
318 |