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[solved]tinyxml bus error

 
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foxss



Joined: 07 Dec 2008
Posts: 6
PostPosted: Wed Dec 23, 2009 2:58 am    Post subject: [solved]tinyxml bus error Reply with quote
Hi,

I tried to parse a utf-8 xml file with tinyxml while get a bus error.
main.cpp
Code:

#include "tinyxml.h"
#include <pspkernel.h>

PSP_MODULE_INFO("sample", 0, 1, 1);
PSP_MAIN_THREAD_ATTR(THREAD_ATTR_USER | THREAD_ATTR_VFPU);
PSP_HEAP_SIZE_KB(20*1024);

TiXmlDocument* doc;

/* Exit callback */
int exit_callback(int arg1, int arg2, void *common) {
    return 0;
}

/* Callback thread */
int CallbackThread(SceSize args, void *argp) {
    int cbid;
    cbid = sceKernelCreateCallback("Exit Callback", exit_callback, NULL);
    sceKernelRegisterExitCallback(cbid);
    sceKernelSleepThreadCB();
    return 0;
}

/* Sets up the callback thread and returns its thread id */
int SetupCallbacks(void) {
    int thid = 0;
    thid = sceKernelCreateThread("update_thread", CallbackThread, 0x11, 0xFA0, PSP_THREAD_ATTR_USER, 0);
    if(thid >= 0)
        sceKernelStartThread(thid, 0, 0);
    return thid;
}

bool LoadMenu(){
  doc = new TiXmlDocument("test.xml");
  return doc->LoadFile();
}


void GenUI(TiXmlElement *elem){
    return;
}

void ParseMenu(TiXmlDocument* doc1){
 
  TiXmlElement* ele = doc1->FirstChildElement("Item");
  do{
    GenUI(ele);
    ele = ele->NextSiblingElement();
  }while(ele);
 
  return;
}

int main() {
    SetupCallbacks();
   
    if(!LoadMenu()){
        //when config file missing, exit program
        sceKernelExitGame();
        return 0;
    }
    ParseMenu(doc);
    sceKernelExitGame();
    return 0;
}


Code:

host0:/> ./VersiPSP.prx
Load/Start host0:/VersiPSP.prx UID: 0x045EFC39 Name: "s
host0:/> Exception - Bus error (data)
Thread ID - 0x045E7745
Th Name   - user_main
Module ID - 0x045EFC39
Mod Name  - "sample"
EPC       - 0x088047D4
Cause     - 0x1000001C
BadVAddr  - 0x10500440
Status    - 0x40088613
zr:0x00000000 at:0xDEADBEEF v0:0x00000001 v1:0x00000A59
a0:0x00000000 a1:0x00000021 a2:0x00000A58 a3:0x08828984
t0:0x00000020 t1:0x088355A8 t2:0x0882DDF8 t3:0x088355BC
t4:0x00000000 t5:0xDEADBEEF t6:0xDEADBEEF t7:0xDEADBEEF
s0:0x00000000 s1:0x08835330 s2:0x00000001 s3:0x0BBBFEE0
s4:0x00000014 s5:0x00000013 s6:0xDEADBEEF s7:0xDEADBEEF
t8:0xDEADBEEF t9:0xDEADBEEF k0:0x0BBBFF00 k1:0x00000000
gp:0x088364A0 sp:0x0BBBFE08 fp:0x0BBBFEA0 ra:0x08804454
0x088047D4: 0x8C83001C '....' - lw         $v1, 28($a0)


Is someone know what this about?
I can't get clue over this.

Thanks,
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Last edited by foxss on Mon Dec 28, 2009 12:31 pm; edited 1 time in total
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psPea



Joined: 01 Sep 2007
Posts: 64
PostPosted: Wed Dec 23, 2009 5:12 am    Post subject: Reply with quote
You're trying to derefeence a null pointer at 0x3d4

lw $v1, 28($a0)
a0:0x00000000
EPC:0x088047D4

lw destinationRegister, offset(sourceRegester) # load contents of RAM at offset from sourceRegister into register destinationRegister: destinationRegister = *(destinationRegister+offset)

To calculate where the error occurs type in psplink
calc $epc-$mod
then use that address in psp-address
psp-address2line -fCe your_module.elf address
This will give you the file and the line the error occurs(for this to work need to have -g in CFLAGS in your makefile)


Okay I see 2 places where your crash could have happened
return doc->LoadFile();
ele = ele->NextSiblingElement();

Edit:
I'll go with "return doc->LoadFile();" since LoadFile() is the 8th member of TiXmlDocument. You should make sure you classes are created before you use them.
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foxss



Joined: 07 Dec 2008
Posts: 6
PostPosted: Wed Dec 23, 2009 4:37 pm    Post subject: Reply with quote
Thanks, psPea!

I finally find crash caused as ele is a null pointer. I should be more defensive, check it before using...
Code:

ele = ele->NextSiblingElement();


psPea wrote:
You're trying to derefeence a null pointer at 0x3d4

lw $v1, 28($a0)
a0:0x00000000
EPC:0x088047D4

lw destinationRegister, offset(sourceRegester) # load contents of RAM at offset from sourceRegister into register destinationRegister: destinationRegister = *(destinationRegister+offset)

To calculate where the error occurs type in psplink
calc $epc-$mod
then use that address in psp-address
psp-address2line -fCe your_module.elf address
This will give you the file and the line the error occurs(for this to work need to have -g in CFLAGS in your makefile)


Okay I see 2 places where your crash could have happened
return doc->LoadFile();
ele = ele->NextSiblingElement();

Edit:
I'll go with "return doc->LoadFile();" since LoadFile() is the 8th member of TiXmlDocument. You should make sure you classes are created before you use them.

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Love eReader/XReader
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