diff options
| -rw-r--r-- | ChangeLog | 4 | ||||
| -rw-r--r-- | doc/FileSystem.3 | 30 | ||||
| -rw-r--r-- | generic/tclIOUtil.c | 13 |
3 files changed, 33 insertions, 14 deletions
@@ -14,7 +14,9 @@ * doc/FileSystem.3: cleaned up internal handling of Tcl_FSOpenFileChannel to remove duplicate code, and make writing external vfs's clearer and easier. No - functionality change. + functionality change. Also clarify that objects with refCount + zero should not be passed in to the Tcl_FS API, and prevent + segfaults from occuring on such user errors. [Bug 578617] 2002-07-06 Don Porter <dgp@users.sourceforge.net> diff --git a/doc/FileSystem.3 b/doc/FileSystem.3 index 0161dba..d4f4c25 100644 --- a/doc/FileSystem.3 +++ b/doc/FileSystem.3 @@ -4,7 +4,7 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: FileSystem.3,v 1.28 2002/07/08 10:14:24 vincentdarley Exp $ +'\" RCS: @(#) $Id: FileSystem.3,v 1.29 2002/07/08 12:08:34 vincentdarley Exp $ '\" .so man.macros .TH Filesystem 3 8.4 Tcl "Tcl Library Procedures" @@ -257,17 +257,23 @@ declared to be, allowing the same code to be used both on systems with and systems without support for files larger than 2GB in size. .PP The \fBTcl_FS...\fR are objectified and may cache internal -representations and other path-related strings (e.g. the current -working directory). One side-effect of this is that one must be -careful when passing in temporary objects with a refCount of zero. -Under some circumstances, the filesystem code may wish to retain a -reference to the passed in object, and so one must not assume that -after any of these calls return, the object still has a refCount of -zero - it may have been incremented. The practical lesson to learn -from this is that \fBTcl_Obj *path = Tcl_NewStringObj(...) ; -Tcl_FS...(path) ; Tcl_DecrRefCount(path)\fR is wrong, and may -segfault. The 'path' must have its refCount incremented before -passing it in, or decrementing it. +representations and other path-related strings (e.g. the current working +directory). One side-effect of this is that one must not pass in objects +with a refCount of zero to any of these functions. If such calls were +handled, they might result +in memory leaks (under some circumstances, the filesystem code may wish +to retain a reference to the passed in object, and so one must not assume +that after any of these calls return, the object still has a refCount of +zero - it may have been incremented), or in a direct segfault +due to the object being freed part way through the complex object +manipulation required to ensure that the path is fully normalized and +absolute for filesystem determination. The practical lesson to learn +from this is that \fBTcl_Obj *path = Tcl_NewStringObj(...) ; +Tcl_FS...(path) ; Tcl_DecrRefCount(path)\fR is wrong, and may segfault. +The 'path' must have its refCount incremented before passing it in, or +decrementing it. For this reason, objects with a refCount of zero are +considered not to be valid filesystem paths and calling any Tcl_FS API +with such an object will result in no action being taken. .PP \fBTcl_FSCopyFile\fR attempts to copy the file given by srcPathPtr to the path name given by destPathPtr. If the two paths given lie in the same diff --git a/generic/tclIOUtil.c b/generic/tclIOUtil.c index d779b5c..d273e6c 100644 --- a/generic/tclIOUtil.c +++ b/generic/tclIOUtil.c @@ -17,7 +17,7 @@ * See the file "license.terms" for information on usage and redistribution * of this file, and for a DISCLAIMER OF ALL WARRANTIES. * - * RCS: @(#) $Id: tclIOUtil.c,v 1.53 2002/07/08 10:11:22 vincentdarley Exp $ + * RCS: @(#) $Id: tclIOUtil.c,v 1.54 2002/07/08 12:08:34 vincentdarley Exp $ */ #include "tclInt.h" @@ -4757,6 +4757,17 @@ Tcl_FSGetFileSystemForPath(pathObjPtr) Tcl_Filesystem* retVal = NULL; FsPath* srcFsPathPtr; + /* + * If the object has a refCount of zero, we reject it. This + * is to avoid possible segfaults or nondeterministic memory + * leaks (i.e. the user doesn't know if they should decrement + * the ref count on return or not). + */ + + if (pathObjPtr->refCount == 0) { + return NULL; + } + /* Make sure pathObjPtr is of our type */ if (Tcl_FSConvertToPathType(NULL, pathObjPtr) != TCL_OK) { |