Hello,
I'm trying to display a menu on my device, with str710 mcu. To do that, I create use structs to hold the variables and display them later. My structs look like this:
typedef const struct mMenu_s { int type; char text[3][20]; struct command { int command; int argument; } commands; struct specialline { int een; int twee; int drie; } speciallines; } menutype; typedef struct sMenuTemp { menutype *mCurmenu[20]; int iCurmenu; int iCurmenupos; int iOldmenu; int iOldmenupos; int menuactive; } cmdMenu; extern cmdMenu sMenu;
And to place data in it I use:
cmdMenu sMenu; menutype Backlightmenu[] = { { 1, {"Rood", "Red", "Rot"}, {SET_BACKLIGHT,RED}, {NULL,NULL,NULL} }, { 2, {"Groen", "Green", "Grun"}, {SET_BACKLIGHT,GREEN}, {NULL,NULL,NULL} }, { 3, {"Wit", "White", "Weiss"}, {SET_BACKLIGHT,WHITE}, {NULL,NULL,NULL} }, { NULL } }; sMenu->mCurmenu[BACKLIGHTMENU] = Backlightmenu;
With this method I can let (other) programmers create/delete/edit a menu very easy. So far so good.. All the text, commands, arguments and the rest of variables are stored in the memory OK (checked the memory watch, all OK!). But then.. I wan't to display the texts. Selecting the menu, the menuline, the language and the text is no problem. But, with the displaying, the last line of my struct is getting destroyed.
I've debugged my program, and it seems that the LCD-library caused the problem. It does an integer division, and the assembly calls "__aeabi_idivmod", which is an divide-function. On the first instruction, which is: PUSH {R4-R6,LR}, the data of my struct get destroyed, and it very, very weird values on the place of the struct..
And, the stupid thing.. When I remove the graphic-function, it's all normal. And, it doesn't matter on what memory-location my struct is placed, it happens every time.. It looks like the divide haunts my struct =S.
I'm working with the MDK-Arm 3.70 toolchain, in uVision3. Does anybody have an idea why this happens? Or, even better, the solution? I've tried a lot of other things, but it would be so d*mn easy to build and display my menu like that...
Thank you so very much.
Jay.
You don't really give us much to go on there. What is that LCD library code actually doing at the point of the corruption? Is it, by any chance, working on some of the data contained in that struct? Why would it be performing a division in the first place? And what do you mean when you say:
the last line of my struct is getting destroyed
What gets written where?
Without answers to those questions, I can only offer some general comments.
*) Please don't write NULL when you mean integer zero. NULL should be used for data pointers only.
*) It may not be too wise to put your menu texts directly into the struct, as arrays insetad of pointers to string literals. That's a waste of memory, and likely to create nasty effects if anybody ever configures a string longer than 19 characters.
*) Have you checked for possible stack overrun?
Thank you for your replie(s). I've changed my code/struct a little bit. I've removed the two structs in the sMenuField-struct. I've also changed the array into a multi-dimensional pointer-array. Now it's like this:
typedef struct sMenuField { int type; char *text[3]; int commands[2]; int speciallines[4]; } MenuFieldtype; typedef struct sMenu { MenuFieldtype *mCurmenu[20]; int iCurmenu; int iCurmenupos; int iOldmenu; int iOldmenupos; int menuactive; } cmdMenu;
But still.. Same problem.. The struct that's holding the pointers gets changed by the graphic library. Not on the divide-part now, but just on a variable-assignment in C. The disassembly says:
0x20002D58 B4FF PUSH {R0-R7}
Register R0 and R7 both holds 0x00000000.
I've created two screenshots to clear up the effect of the instruction.. The first one is a screenie of the memorywatch, after creating the struct and place my data in it. I've marked the part that holds the last line of the menu. The second one is the screenie right after the PUSH-instruction. Again I've marked the part that it's all about. As you can see, there is nothing (recognizable) left.
img406.imageshack.us/.../memorybeforepush.jpg img294.imageshack.us/.../memoryafterpush.jpg
*) I've checked for a stack-overrun; not possible. The're just a few things on the stack.. The MCU must be capable of handling this..
*) I've changed to NULL to integer zero (or another logical integer.)
*) As you can see, the text is stored in a pointer. That is working very well. The text is not getting touched by the instructions. It's just the struct that holds it all together..
It's so weird.. It's always the last line.. -.-. And it's also always a PUSH-instruction that destroyes the last line.. Does anybody have any idea?
Thank you very, very much!!
you can instruct the debugger to stop when a specific memory location is read/written. maybe this can help you detect what modifies your struct.
Thank you for you reply..
But.. Euh.. I already know where my struct gets modified.. And by what instruction.. It's getting modified by the PUSH-instruction..
But, i'm curious. How can I do that, what you suggested?
Thanks!
Debug->Breakpoints->Access
Don't forget to specify the size and bytes/objects, and of course the expression to be evaluated. that can also be a memory address, of course.
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