I am using VS2017 and have the following lines of C code (sorry can't post all contents of function):
char *dptr; /* Global variables */
static u_int16_t vers;
...
static int32_t
read_row(database_t *dbase, table_t *table, int32_t col_flag, int32_t flag) {
row_t *rowptr;
char marker;
void *new_row;
table_t *t_new;
size_t row_length;
size_t row_ = 1;
marker = *dptr++;
if (vers < VERS && marker != ROW) {
return -1;
}
/* Create a new row */
t_new = table;
row_length = t_new->row_length;
new_row = calloc(row_, row_length);
rowptr = new_row;
if (rowptr == NULL)
return -1;
...
The last line is causing "Exception thrown at 0x00000000778745A0 (ntdll.dll) in ****.exe: 0xC0000005: Access violation reading location 0x00000000787745A0" error.
During debug, when I hover my pointer on calloc, I can see its value is "0x000000013f63dc94". But somehow, the exception is thrown and this value is never assigned to new_row (its value remains "0xcccccccccccccccc").
I have noticed that this exception is thrown when calloc has a value >"0x00000001********". It seems to work fine if 8 MSB of the address are 0.
The definition of calloc() is from corecrt.malloc.h:
_Check_return_ _Ret_maybenull_ _Post_writable_byte_size_(_Count * _Size)
_ACRTIMP _CRT_JIT_INTRINSIC _CRTALLOCATOR _CRTRESTRICT
void* __cdecl calloc(
_In_ _CRT_GUARDOVERFLOW size_t _Count,
_In_ _CRT_GUARDOVERFLOW size_t _Size
);
Any ideas about what could be causing this exception and how to fix it would be appreciated. Btw, I am using Win 7 Pro with 8GB RAM.
Related
I'm struggling with an issue where an ESP32 is running as a AP with AsyncTCP connecting multiple ESP32 clients. The AP receives some JSON data and replies with some JSON data. Without the handleData() function, the code runs 100% fine with no issues. Heap is static when no clients connect and issues only occur when clients start connecting.
Can anyone see anything with my code that could be causing heap corruption or other memory weirdness?
static void handleData(void* arg, AsyncClient* client, void *data, size_t len) {
int i = 0, j = 0;
char clientData[CLIENT_DATA_MAX];
char packetData[len];
char *packetBuf;
packetBuf = (char *)data;
clientData[0] = '\0';
for (i=0;i <= len;i++) {
packetData[j] = packetBuf[i]; //packetBuf[i];
if ((packetData[j] == '\n') || (i == len)) {
packetData[j] = '\0';
if ((j > 0) && (packetData[0] != '\n') && (packetData[0] != '\r')) {
// See sensorData() below...
parseData.function(packetData, clientData);
if (clientData != NULL) {
// TCP reply to client
if (client->space() > 32 && client->canSend()) {
client->write(clientData);
}
}
}
j = 0;
} else
j++;
}
}
void sensorData(void *data, void *retData) {
StaticJsonDocument<CLIENT_DATA_MAX> fields;
StaticJsonDocument<CLIENT_DATA_MAX> output;
char sensor[15] = "\0";
char MAC[18] = "\0";
char value[20] = "\0";
bool sendOK = false;
memcpy((char *)retData, "\0", 1);
DeserializationError error = deserializeJson(fields, (char *)data, CLIENT_DATA_MAX);
if (error) {
DEBUG_PRINTLN(F("deserializeJson() failed"));
return;
}
if (fields["type"])
strcpy(sensor, fields["type"]);
switch (sensor[0]) {
case 'C':
if (fields["value"])
strcpy(value, fields["value"]);
sendOK = true;
break;
case 'T': //DEBUG_PRINT(F("Temp "));
setExtTempSensor(fields["value"]);
sendOK = true;
break;
case 'N':
output["IT"] = intTempC; //Internal temp
output["B1"] = battLevels[0];
serializeJson(output, (char *)retData, CLIENT_DATA_MAX-1);
break;
}
if (sendOK) {
output["Resp"] = "Ok";
serializeJson(output, (char *)retData, CLIENT_DATA_MAX-1);
}
strcat((char *)retData, "\n");
}
static void handleNewClient(void* arg, AsyncClient* client) {
client->setRxTimeout(1000);
client->setAckTimeout(500);
client->onData(&handleData, NULL);
client->onError(&handleError, NULL);
client->onDisconnect(&handleDisconnect, NULL);
client->onTimeout(&handleTimeOut, NULL);
}
void startServer() {
server = new AsyncServer(WIFI_SERVER_PORT);
server->onClient(&handleNewClient, &server)
}
Using AsyncTCP on the ESP32 was having multiple issues. Heap issues, socket issues, assert issues, ACK timeouts, connection timeouts, etc. Swapping to AsyncUDP using the exact same code as shown above with romkey's changes, resolved all of my issues. (Just using romkey's fixes did not fix the errors I was having with AsyncTCP.) I don't believe the issue is with AsyncTCP but with ESP32 libraries.
Either you should declare packetData to be of length len + 1 or your for loop should iterate until i < len. Because the index starts at 0, packetData[len] is actually byte len + 1, so you'll overwrite something random when you store something in packetData[len] if the array is only len chars long.That something random may be the pointer stored in packetBuf, which could easily cause heap corruption.
You should always use strncpy() and never strcpy(). Likewise use strncat() rather than strcat(). Don't depend on having done the math correctly or on sizes not changing as your code evolves. strncpy() and strncat() will guard against overflows. You'll need to pass a length into sensorData() to do that, but sensorData() shouldn't be making assumptions about the available length of retData.
Your test
if (clientData != NULL) {
will never fail because clientData is the address of array and cannot change. I'm not sure what you're trying to test for here but this if will always succeed.
You can just write:
char sensor[15] = "";
you don't need to explicitly assign a string with a null byte in it.
And
memcpy((char *)retData, "\0", 1);
is equivalent to
((char *)retData)[0] = '\0';
What's the point of declaring retData to be void * in the arguments to sensorData()? Your code starts out with it being a char* before calling sensorData() and uses it as a char* inside sensorData(). void * is meant to be an escape hatch for passing around pointers without worrying about their type. You don't need that here and end up needing to extra casts back to char* because of it. Just declare the argument to be char* and don't worry about casting it again.
You didn't share the code that calls handleData() so there may well be issues outside of these functions.
I'm working on an Arduino project where I need to build (and work with) a two-dimensional array at runtime. I've been poking around looking for a solution, but I've had no luck. I found an example of a dynamic one-dimentional array helper here: http://playground.arduino.cc/Code/DynamicArrayHelper, so i've been trying to adopt that code for my use. I created a library using the following code:
My Header file:
#ifndef Dynamic2DArray_h
#define Dynamic2DArray_h
#include "Arduino.h"
class Dynamic2DArray
{
public:
Dynamic2DArray( bool sorted );
//Add an integer pair to the array
bool add( int v1, int v2);
//Clear out (empty) the array
bool clear();
//Get the array item in the specified row, column
int getValue(int row, int col);
//Get the number of rows in the array
int length();
private:
int _rows;
void * _slots;
bool _sorted;
void _sort();
};
#endif
The library's code:
#include "Arduino.h"
#include "Dynamic2DArray.h"
#define ARRAY_COLUMNS 2
int _rows;
void * _slots;
bool _sorted;
Dynamic2DArray::Dynamic2DArray(bool sorted) {
//Set our local value indicating where we're supposed to
//sort or not
_sorted = sorted;
//Initialize the row count so it starts at zero
_rows = 0;
}
bool Dynamic2DArray::add( int v1, int v2) {
//Add the values to the array
//implementation adapted from http://playground.arduino.cc/Code/DynamicArrayHelper
//Allocate memory based on the size of the current array rows plus one (the new row)
int elementSize = sizeof(int) * ARRAY_COLUMNS;
//calculate how much memory the current array is using
int currentBufferSize = elementSize * _rows;
//calculate how much memory the new array will use
int newBufferSize = elementSize * (_rows + 1);
//allocate memory for the new array (which should be bigger than the old one)
void * newArray = malloc ( newBufferSize );
//Does newArray not point to something (a memory address)?
if (newArray == 0) {
//Then malloc failed, so return false
return false;
}
// copy the data from the old array, to the new array
for (int idx = 0; idx < currentBufferSize ; idx++)
{
((byte*)newArray)[idx] = ((byte *)_slots)[idx];
}
// free the original array
if (_slots != NULL)
{
free(_slots);
}
// clear the newly allocated memory space (the new row)
for (int idx = currentBufferSize; idx < newBufferSize; idx++)
{
((byte *)newArray)[idx] = 0;
}
// Store the number of rows the memory is allocated for
_rows = ++_rows;
// set the array to the newly created array
_slots = newArray;
//Free up the memory used by the new array
free(newArray);
//If the array's supposed to be sorted,
//then sort it
if (_sorted) {
_sort();
}
// success
return true;
};
int Dynamic2DArray::length() {
return _rows;
};
bool Dynamic2DArray::clear() {
//Free up the memory allocated to the _slots array
free(_slots);
//And zero out the row count
_rows = 0;
};
int Dynamic2DArray::getValue(int row, int col) {
//do we have a valid row/col?
if ((row < _rows) && (col < ARRAY_COLUMNS)) {
//Return the array value at that row/col
return _slots[row][col];
} else {
//No? Then there's nothing we can do here
return -1;
}
};
//Sorted probably doesn't matter, I can probably ignore this one
void _sort() {
}
The initial assignment of the _slots value is giving me problems, I don't know how to define it so this code builds. The _slots variable is supposed to point to the dynamic array, but I've got it wrong.
When I try to compile the code into my project's code, I get the following:
Arduino: 1.8.0 (Windows 10), Board: "Pro Trinket 3V/12MHz (USB)"
sketch\Dynamic2DArray.cpp: In member function 'int Dynamic2DArray::getValue(int, int)':
sketch\Dynamic2DArray.cpp:83:22: warning: pointer of type 'void *' used in arithmetic [-Wpointer-arith]
return _slots[row][col];
^
Dynamic2DArray.cpp:83: error: 'void*' is not a pointer-to-object type
Can someone please help me fix this code? I've posted the files to https://github.com/johnwargo/Arduino-Dynamic-2D-Array-Lib.
The code you took was for a 1D dynamic array; the modifications for a 2D array are too tricky. Give up these horrors.
I think there is no reason you use dynamic array. You can assume that size max is ROW_MAX * COL_MAX, so you can define a static array int array[ROW_MAX][COL_MAX].
on one hand if you defined a dynamic array, you could free space when you dont use it anymore and take advantage of it for other work. I dont know if this is your case.
on the other hand if you define a static array (on UNO), you have 32kB available on program space, instead of 2kB available on RAM.
Because of the difference 32kB / 2kB, there are very few chances you can get bigger array with dynamic allocation.
so i know the bases of programming, i have a decent amount of experience with java, but im learning C for school right now. I still dont completely understand the whole pointer aspect, which is what im sure caused the fault. This program works fine when run on my computer, but when i try and run it on my schools unix shell it gives me a seg fault. if someone could please explain to me why or how ive misused hte pointers, that would help me greatly.
//Matthew Gerton
//CS 222 - 002
//10/10/14
//HW Six
//libraries
#include<stdio.h>
#include<string.h>
#define max_Length 256
//prototypes
void decode(char *a, char *b);
void trimWhite(char *a);
void encode(char *a, char *b);
int main(void)
{
//character arrays
char coded[max_Length], decoded[max_Length];
//decode the sample phrase
char sample[] = {'P','H','H','W','D','W','C','R','R','F','D','Q','F','H','O','H','G','J',
'R','W','R','P','H','W','U','R','K','R','W','H','O','U','R','R','P','I','R','X','U'};
decode(sample, decoded);
//scans a user input string to decode, and decodes it
printf("\nPlease enter a phrase to decode: ");
gets(coded);
trimWhite(coded);
decode(coded, decoded);
//scans a user input phrase to encode
printf("\nPlease enter a phrase to encode: ");
gets(coded);
trimWhite(coded);
encode(coded, decoded);
}
//removes any spaces from the input
void trimWhite(char *a)
{
char temp[max_Length];
int z=0, y=0;
while(a[z]!='\0')
{
if(a[z]!=' ')
{
temp[y]=a[z];
y++;
}
z++;
}
temp[y] = '\0';
strcpy(a,temp);
}
//decodes any phrase
void decode(char *a, char *b)
{
int i=0,n;
memset(b, '\0', sizeof(b));
while(a[i]!='\0')
{
n=(int)a[i];
if(n<97)
n=n+32;
if(n<=99)
n=n+23;
else
n = n-3;
b[i]= (char) n;
i++;
}
b[i]='\0';
printf("Coded message: %s\n", a);
printf("Decoded message: %s\n", b);
}
//codes an input phrase
void encode(char *a, char *b)
{
int i=0,n;
memset(b, '\0', sizeof(b));
strcpy(b,a);
while(a[i]!='\0')
{
n=(int)a[i];
if(n<97)
a[i] = (char)(n+32);
if((n>120)
a[i] = (char)(n-23);
else
a[i] = (char)((n+3);
i++;
}
printf("Coded message: %s\n", a);
}
Your main problem is here:
char sample[] = {'P','H','H', /* snip */ ,'R','X','U'};
The sample[] array is not zero-terminated which may cause the decode() function to copy many more characters than intended, thus overwriting other variables. You need to explicitly add a terminating zero when using an initializer-list:
char sample[] = {'P','H','H', /* ... */ ,'R','X','U',0};
Or you can initialize the array using a string literal, which does include a terminating zero:
char sample[] = "PHHWDWCRRFDQFHOHGJRWRPHWURKRWHOURRPIRXU";
You should probably read "Why is the gets function dangerous".
...
void decode(char *a, char *b)
{
int i=0,n;
memset(b, '\0', sizeof(b));
Also note that the size of the array is lost when it is passed to a function. The function only receives a pointer to its first element. The memset() call above will only zero sizeof(char*) bytes (usually 4 or 8). This doesn't matter though because, as far as I can tell, you only need to zero the first byte. You could simply write:
b[0] = 0;
This is a follow-up to the post here - Writting data to the Arduino's onboard EEPROM
I just tried using the snippets in the URL but wouldn't work. Please help me fix the below error.
write_to_eeprom.cpp:8:5: error: expected unqualified-id before '[' token
write_to_eeprom.cpp: In function 'void setup()':
write_to_eeprom.cpp:12:16: error: 'stringToWrite' was not declared in this scope
write_to_eeprom.cpp: In function 'void loop()':
write_to_eeprom.cpp:22:33: error: invalid conversion from 'uint8_t {aka unsigned char}' to 'char*' [-fpermissive]
write_to_eeprom.cpp: In function 'void EEPROM_write(void*, byte)':
write_to_eeprom.cpp:32:32: error: 'void*' is not a pointer-to-object type
Here is the code
#include <EEPROM.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 13, 9, 4, 5, 6, 7);
char[] stringToWrite = "Test";
void setup() {
lcd.begin(16, 2);
delay(5000);
EEPROM_write(stringToWrite, strlen(stringToWrite));
}
void loop() {
delay(10000);
int addr = 0;
byte datasize = EEPROM.read(addr++);
char stringToRead[0x20]; // allocate enough space for the string here!
char * readLoc = stringToRead;
for (int i=0;i<datasize; i++) {
readLoc = EEPROM.read(addr++);
readLoc++;
}
}
// Function takes a void pointer to data, and how much to write (no other way to know)
// Could also take a starting address, and return the size of the reach chunk, to be more generic
void EEPROM_write(void * data, byte datasize) {
int addr = 0;
EEPROM.write(addr++, datasize);
for (int i=0; i<datasize; i++) {
EEPROM.write(addr++, data[i]);
}
}
Well, you need to fix your code:
line 8 -- [] needs to go AFTER stringToWrite
line 12 -- should get better after fixing line 8
line 22 -- you need to dereference readLoc. add a '*' before it.
line 32 -- your parameter "data" is a pointer to void, which has no size. Because of that, you will not be able to use it as an array. You could change the declaration to:
void EEPROM_write(char * data, byte datasize)
That fixes the compiler errors. Taking a quick look at the semantics of the code seems to be doing what you want. Good luck.
I couldn't find a reason for this problem.
The function getfruits returns a pointer to an array of pointes of c-style strings.
Main tries to access the c-style strings.
using namespace System;
#pragma managed
void getfruits(char ***list, int* count)
{
char *txt[] =
{
"apple",
"orange",
"pears",
"banana",
};
*list = txt;
*count = 4;
}
#pragma managed
int main(array<System::String ^> ^args)
{
char **lst; int cnt;
getfruits(&lst,&cnt);
char *t; int i;
String^ s;
for (i=0; i<cnt; i++)
{
t = lst[i]; //t = <undefined value>
s = gcnew String(t);
Console::WriteLine("Fruit = {0}", s);
};
Console::ReadKey();
return 0;
}
But it gets instead of pointers to the c-style strings.
Eventually,
An unhandled exception of type 'System.AccessViolationException' occurred in arraysandclasses.exe
Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
What's going wrong? Can somebody point out anything? The code should simply compile if copied and pasted. Thanks in advance.
You've returned the address of a local array and used it. That's undefined behavior. txt has automatic storage duration and gets destroyed as soon as you leave the getfruit function. But you keep a pointer to it and use it, but the pointed memory no longer contains a living object. I suggest that you should perhaps read a good C++ book.