xg00@GTE.COM (Xev Gittler) (05/26/89)
Could someone perhaps tell me what I am doing wrong? Reading the
documentation on XtAppCreateShell, this seems to be what I am supposed
to do, but it is not working. I keep getting an
X Toolkit Error: Cannot perform malloc
The following is the code. It gets the error on the XtAppCreateShell
command. If anyone can help me out, I would REALLY appreciate it!
Xev Gittler
xg00@gte.com, or
xg00%gte.com@relay.cs.net
#include <X11/Xlib.h>
#include <X11/Intrinsic.h>
#include <X11/StringDefs.h>
#include <X11/Command.h>
main(argc,argv)
int argc;
char *argv[];
{
XtAppContext MyApplicationContext;
Widget TopLevel, mybutton;
Display *TheXDisplay;
int n;
Arg args[20];
XtToolkitInitialize();
MyApplicationContext = XtCreateApplicationContext();
TheXDisplay = XtOpenDisplay (MyApplicationContext, NULL, "Xtest",
"Xtest", NULL, 0, &argc, argv);
TopLevel = XtAppCreateShell (NULL, "Xtest",
"applicationShellWidgetClass", TheXDisplay,
NULL, 0);
n = 0;
XtSetArg (args[n], XtNwidth, 200); n++;
XtSetArg (args[n], XtNlabel, "Blah!!"); n++;
mybutton = XtCreateManagedWidget ("TopLabel", commandWidgetClass,
TopLevel, args, n);
XtRealizeWidget (TopLevel);
XtMainLoop();
}
--
Xev Gittler
xg00@gte.com, or
xg00%gte.com@relay.cs.netconverse@EXPO.LCS.MIT.EDU (Donna Converse) (05/26/89)
> Could someone perhaps tell me what I am doing wrong? > I keep getting an > X Toolkit Error: Cannot perform malloc The error message doesn't really tell you anything, I agree. 1) You don't need to include X11/Xlib.h, but you must include X11/Shell.h 2) In the call to XtAppCreateShell, the widget class parameter should not be quoted. (Maybe you tried quoting it after you got an error because Shell.h was not included; it is defined in Shell.h) Generally, for every class of widget that you instantiate, there is a required include file. These first two caused the error message. Finally, to get it flying: 3) Replace XtMainLoop() with XtAppMainLoop(MyApplicationContext) Donna Converse MIT X Consortium
kit@EXPO.LCS.MIT.EDU (Chris D. Peterson) (05/26/89)
Donna's reply covered the problem I think, but there is another thing
or two in here just waiting to bite you...
XtOpenDisplay() can return NULL if it is not able to open the display, if you
try to pass NULL to XtAppCreateShell() it will probabally seg. fault. You
need to check this value to make sure that a non-NULL display is returned.
Also, it is usually best to pass NULL as the name of the application, this
will cause the toolkit to look for resources using the last component of
argv[0] as the application name. This is generally the desired behavior.
Chris D. Peterson
MIT X Consortium
Net: kit@expo.lcs.mit.edu
Phone: (617) 253 - 9608
Address: MIT - Room NE43-213smithrd@inteloa.intel.com (Randy D. Smith) (06/03/89)
In article <8905261610.AA17950@expo.lcs.mit.edu> kit@EXPO.LCS.MIT.EDU (Chris D. Peterson) writes: > >Donna's reply covered the problem I think, but there is another thing >or two in here just waiting to bite you... > > Chris D. Peterson > MIT X Consortium Speaking of being bitten by the "Toolkit: cannot malloc" bug... I notice that Xlib has code surrounded by #ifdefs on the preprocessor variable "MALLOC_0_RETURNS_NULL". Very nice for SVIDish systems. I also noticed (via the aforementioned error message) that the toolkit was not quite so, how shall we put it, portable (sigh, I know the word is a bit overworked, but it was the best I could do with such little notice). It would be really nice (pretty please?) if the toolkit (and anything else which becomes a part of "the standard") were at least as portable as Xlib. Perhaps for R4? I have no idea whether this could be the problem the original poster was facing, but if so...just go into Xt/Alloc.c and make sure all the allocation routines check for requests for 0 bytes, and pass on to the libc equivalents requests for 1 (or more) bytes instead. -- Randy D. Smith BiiN (tm), An Information Systems Company ...uunet!tektronix!inteloa!smithrd (503) 696-4660
jlf@earth.cray.COM (John Freeman) (06/05/89)
> I notice that Xlib has code surrounded by #ifdefs on the preprocessor > variable "MALLOC_0_RETURNS_NULL". Very nice for SVIDish systems. I > also noticed (via the aforementioned error message) that the toolkit > was not quite so, > > I have no idea whether this could be the problem the original poster > was facing, but if so...just go into Xt/Alloc.c and make sure all the > allocation routines check for requests for 0 bytes, and pass on to > the libc equivalents requests for 1 (or more) bytes instead. The port of the toolkit by Cray Research does exactly what you suggest in Xt/Alloc.c. Here are the diffs: ------------------------------------------------------------------------------- diff -c ~/X11R3/lib/Xt/Alloc.c . *** /usr/earth3/jlf/X11R3/lib/Xt/Alloc.c Tue Sep 6 15:26:46 1988 --- ./Alloc.c Mon Dec 19 17:37:54 1988 *************** *** 41,46 **** --- 41,47 ---- unsigned size; { char *ptr; + if (size == 0) size = 1; if ((ptr = malloc(size)) == NULL) XtErrorMsg("allocError","malloc","XtToolkitError", "Cannot perform malloc", (String *)NULL, (Cardinal *)NULL); *************** *** 51,56 **** --- 52,58 ---- char *ptr; unsigned size; { + if (size == 0) size = 1; if (ptr == NULL) return(XtMalloc(size)); else if ((ptr = realloc(ptr, size)) == NULL) XtErrorMsg("allocError","realloc","XtToolkitError", *************** *** 62,67 **** --- 64,73 ---- unsigned num, size; { char *ptr; + if ((size == 0) || (num == 0)) { + size = 1; + num = 1; + } if ((ptr = calloc(num, size)) == NULL) XtErrorMsg("allocError","calloc","XtToolkitError", "Cannot perform calloc", (String *)NULL, (Cardinal *)NULL);