I am working on an application, where if this certain error message is given, it is ignored:
[Oracle][ODBC][Ora]ORA-24338: statement handle not executed
My code for comparison is the following:
char Sqlstate[10];
long NativeErrorPtr;
char MessageText[1024];
long BufferLength=1024;
long TextLengthPtr;
SQLGetDiagRec(SQL_HANDLE_STMT,sqlc.g_hstmt,1,(SQLCHAR *) Sqlstate,(SQLINTEGER *) &NativeErrorPtr,
(SQLCHAR *) MessageText,(SQLSMALLINT) BufferLength,(SQLSMALLINT *) &TextLengthPtr);
success=false;
char* msg = MessageText;
char* oracleMsg = "[Oracle][ODBC][Ora]ORA-24338: statement handle not executed";
int i = strcmp(msg, oracleMsg);
I am getting i ==1. When I hover over both msg and oracleMsg they look exactly the same. Here is the copied text from each variable.
oracleMsg 0x00c1cd88 "[Oracle][ODBC][Ora]ORA-24338: statement handle not executed" char *
msg 0x0132d0a4 "[Oracle][ODBC][Ora]ORA-24338: statement handle not executed" char *
My problem must have been that it is not NULL-terminated. I followed ibre5041's advice and used if((strncmp(msg, oracleMsg, 55))== 0). This only compares the first 55 characters, which avoids the non NULL-terminated issue.
Related
bool sendMessageToGraphics(char* msg)
{
//char ea[] = "SSS";
char* chRequest = msg; // Client -> Server
DWORD cbBytesWritten, cbRequestBytes;
// Send one message to the pipe.
cbRequestBytes = sizeof(TCHAR) * (lstrlen(chRequest) + 1);
if (*msg - '8' == 0)
{
char new_msg[1024] = { 0 };
string answer = "0" + '\0';
copy(answer.begin(), answer.end(), new_msg);
char *request = new_msg;
WriteFile(hPipe, request, cbRequestBytes, &cbRequestBytes, NULL);
}
BOOL bResult = WriteFile( // Write to the pipe.
hPipe, // Handle of the pipe
chRequest, // Message to be written
cbRequestBytes, // Number of bytes to writ
&cbBytesWritten, // Number of bytes written
NULL); // Not overlapped
if (!bResult/*Failed*/ || cbRequestBytes != cbBytesWritten/*Failed*/)
{
_tprintf(_T("WriteFile failed w/err 0x%08lx\n"), GetLastError());
return false;
}
_tprintf(_T("Sends %ld bytes; Message: \"%s\"\n"),
cbBytesWritten, chRequest);
return true;
}
after the first writefile in running (In case of '8') the other writefile function doesn't work right, can someone understand why ?
the function sendMessageToGraphics need to send move to chess board
There are 2 problems in your code:
First of all, there's a (minor) problem where you initialize a string in your conditional statement. You initialize it as so:
string answer = "0" + '\0';
This does not do what you think it does. It will invoke the operator+ using const char* and char as its argument types. This will perform pointer addition, adding the value of '\0' to where your constant is stored. Since '\0' will be converted to the integer value of 0, it will not add anything to the constant. But your string ends up not having a '\0' terminator. You could solve this by changing the statement to:
string answer = std::string("0") + '\0';
But the real problem lies in the way you use your size variables. You first initialize the size variable to the string length of your input variable (including the terminating '\0' character). Then in your conditional statement you create a new string which you pass to WriteFile, yet you still use the original size. This may cause a buffer overrun, which is undefined behavior. You also set your size variable to however many bytes you wrote to the file. Then later on you use this same value again in the next call. You never actually check this value, so this could cause problems.
The easiest way to change this, is to make sure your sizes are set up correctly. For example, instead of the first call, you could do this:
WriteFile(hPipe, request, answer.size(), &cbBytesWritten, NULL);
Then check the return value WriteFile and the value of cbBytesWritten before you make the next call to WriteFile, that way you know your first call succeeded too.
Also, do not forget to remove your sizeof(TCHAR) part in your size calculation. You are never using TCHAR in your code. Your input is a regular char* and so is the string you use in your conditional. I would also advice replacing WriteFile by WriteFileA to show you are using such characters.
Last of all, make sure your server is actually reading bytes from the handle you write to. If your server does not read from the handle, the WriteFile function will freeze until it can write to the handle again.
I'm trying to understand why a segmentation fault (SIGSEGV) occurs during the execution of this piece of code. This error occurs when testing the condition specified in the while instruction, but it does not occur at the first iteration, but at the second iteration.
LPTSTR arrayStr[STR_COUNT];
LPTSTR inputStr;
LPTSTR str;
// calls a function from external library
// in order to set the inputStr string
set_input_str(param1, (char*)&inputStr, param3);
str = inputStr;
while( *str != '\0' )
{
if( debug )
printf("String[%d]: %s\n", i, (char*)str);
arrayStr[i] = str;
str = str + strlen((char*)str) + 1;
i++;
}
After reading this answer, I have done some research on the internet and found this article, so I tried to modify the above code, using this piece of code read in this article (see below). However, this change did not solve the problem.
for (LPTSTR pszz = pszzStart; *pszz; pszz += lstrlen(pszz) + 1) {
... do something with pszz ...
}
As assumed in this answer, it seems that the code expects double null terminated arrays of string. Therefore, I wonder how I could check the contents of the inputStr string, in order to check if it actually contains only one null terminator char.
NOTE: the number of characters in the string printed from printf instruction is twice the value returned by the lstrlen(str) function call at the first iteration.
OK, now that you've included the rest of the code it is clear that it is indeed meant to parse a set of consecutive strings. The problem is that you're mixing narrow and wide string types. All you need to do to fix it is change the variable definitions (and remove the casts):
char *arrayStr[STR_COUNT];
char *inputStr;
char *str;
// calls a function from external library
// in order to set the inputStr string
set_input_str(param1, &inputStr, param3);
str = inputStr;
while( *str != '\0' )
{
if( debug )
printf("String[%d]: %s\n", i, str);
arrayStr[i] = str;
str = str + strlen(str) + 1;
i++;
}
Specifically, the issue was occurring on this line:
while( *str != '\0' )
since you hadn't cast str to char * the comparison was looking for a wide nul rather than a narrow nul.
str = str + strlen(str) + 1;
You go out of bounds, change to
str = str + 1;
or simply:
str++;
Of course you are inconsistently using TSTR and strlen, the latter assuming TCHAR = char
In any case, strlen returns the length of the string, which is the number of characters it contains not including the nul character.
Your arithmetic is out by one but you know you have to add one to the length of the string when you allocate the buffer.
Here however you are starting at position 0 and adding the length which means you are at position len which is the length of the string. Now the string runs from offset 0 to offset len - 1 and offset len holds the null character. Offset len + 1 is out of bounds.
Sometimes you might get away with reading it, if there is extra padding, but it is undefined behaviour and here you got a segfault.
This looks to me like code that expects double null terminated arrays of strings. I suspect that you are passing a single null terminated string.
So you are using something like this:
const char* inputStr = "blah";
but the code expects two null terminators. Such as:
const char* inputStr = "blah\0";
or perhaps an input value with multiple strings:
const char* inputStr = "foo\0bar\0";
Note that these final two strings are indeed double null terminated. Although only one null terminator is written explicitly at the end of the string, the compiler adds another one implicitly.
Your question edit throws a new spanner in the works? The cast in
strlen((char*)str)
is massively dubious. If you need to cast then the cast must be wrong. One wonders what LPTSTR expands to for you. Presumably it expands to wchar_t* since you added that cast to make the code compile. And if so, then the cast does no good. You are lying to the compiler (str is not char*) and lying to the compiler never ends well.
The reason for the segmentation fault is already given by Alter's answer. However, I'd like to add that the usual style of parsing a C-style string is more elegant and less verbose
while (char ch = *str++)
{
// other instructions
// ...
}
The scope of ch is only within in the body of the loop.
Aside: Either tag the question as C or C++ but not both, they're different languages.
Basically I have a buffer in which i am looking for various flags to read certain fields from a binary file format. I have file read into a buffer but as i started to write code to search the buffer for the flags i immediately hit a wall. I am a C++ noob, but here is what i have:
void FileReader::parseBuffer(char * buffer, int length)
{
//start by looking for a vrsn
//Header seek around for a vrns followed by 32 bit size descriptor
//read 32 bits at a time
int cursor = 0;
char vrsn[4] = {'v','r','s','n'};
cursor = this->searchForMarker(cursor, length, vrsn, buffer);
}
int FileReader::searchForMarker(int startPos, int eof, char marker[], char * buffer)
{
int cursor = startPos;
while(cursor < eof) {
//read ahead 4 bytes from the cursor into a tmpbuffer
char tmpbuffer[4] = {buffer[cursor], buffer[cursor+1], buffer[cursor+2], buffer[cursor+3]};
if (strcmp(marker, tmpbuffer)) {
cout << "Found: " << tmpbuffer;
return cursor;
}
else {
cout << "Didn't Find Value: " << marker << " != " << tmpbuffer;
}
cursor = cursor + 4;
}
}
my header looks like this:
#ifndef __FILEREADER_H_INCLUDED__
#define __FILEREADER_H_INCLUDED__
#include <iostream>
#include <fstream>
#include <sys/stat.h>
class FileReader {
public:
FileReader();
~FileReader();
int open(char *);
int getcode();
private:
void parseBuffer(char *, int);
int searchForMarker(int, int, char[], char *);
char *buffer;
};
#endif
I would expect to get back a match for vrsn with strcmp but my result looks like this
Didn't Find Value: vrsn != vrsn
Found:
It looks like it finds it on the second pass after its passed the char array i am looking for.
Relevant hexcode
Your problem is two-fold:
strcmp returns "0" on success, not on failure. Read the documentation.
strcmp expects null-terminated strings. You say that you have chosen non-terminated char arrays because that's what your DB library uses. Well, fine. But still, you are violating the requirements of strcmp. Use strncmp instead (which takes a length argument) or, preferably, actually write C++ and start using std::vector<char> and friends.
Shouldn't that be something like int FileReader::searchForMarker(...) { .... }?
For the second query, I guess the strcmp works when it has two null terminated strings as its arguments. For example str1[]="AAA"; and str2[]="AAA"; then strcmp() would be used as
if(strcmp(str1,str2)==0) which will return 0 to indicate that they are equal. In your case, the tmpbuffer that you have created is not a null terminated string unless you add \0 in the end.So you might want to add \0 in the end of your tmpbuffer to create a string of 'v' 'r' 'n' 's'.
char vrsn[4] = {'v','r','s','n'};
Contains only the 4 characters specified. There is no room for a null character at the end.
char tmpbuffer[4] = {buffer[cursor], buffer[cursor+1], buffer[cursor+2], buffer[cursor+3]};
Contains only the 4 characters from buffer. There is no room for a null character at the end.
Eventually you call:
if (strcmp(marker, tmpbuffer)) {
The strcmp() function expects each of its parameters to end with a null character ('\0'). It wants to work with strings, which are null terminated.
Since your data is not null terminated, you probably want to use memcmp() instead of strcmp().
Also, strcmp() returns zero when its arguments are equal, so the condition in the if statement is inverted. (Zero is false, everything else is true.) The memcmp() function will also return zero when its arguments are equal.
I'm trying to compile some code, but I'm getting an error:
Error invalid conversion from DWORD to const char *
Here's the code I'm trying to compile:
hWindow = FindWindow(NULL, "Window");
if (hWindow){
GetWindowThreadProcessId(hWindow, &pid);
}
hProcess = OpenProcess(PROCESS_ALL_ACCESS, 0, pid);
if(hProcess != NULL) {
SetWindowText(GetDlgItem(MyWindow, MyStatic), pid);
}
How do I convert a DWORD to a const char *?
SetWindowText expects a const char * (i.e. a C-string) and you are passing it a number (pid), it's obvious that you get an error.
The standard C++ way to perform the conversion is to use a string stream (from header <sstream>:
std::ostringstream os;
os<<pid;
SetDlgItemText(MyWindow, MyStatic, os.str().c_str());
(here I used SetDlgItemText instead of GetDlgItem+SetWindowText to save typing, but it's the same thing)
Alternatively, you can use snprintf.
char buffer[40];
snprintf(buffer, sizeof(buffer), "%u", pid);
SetDlgItemText(MyWindow, MyStatic, buffer);
In this line
SetWindowText(GetDlgItem(MyWindow, MyStatic), pid);
pid is a DWORD (as you used it in GetWindowThreadProcessId(hWindow, &pid) which takes a LPDWORD as the second argument). However, SetWindowText expects a C-string as it's second argument, so instead of pid, you must pass a value of type char * or char [].
To display the value of pid, you can make use of sprintf:
char * str = new char[10];
sprintf(str,"%d",pid);
You may have to modify the size of str a little (10 might be too small, or bigger than necessary - that's up to you and your situation).
I have a,
int main (int argc, char *argv[])
and one of the arguements im passing in is a char. It gives the error message in the title when i go to compile
How would i go about fixing this?
Regards
Paul
When you pass command line parameters, they are all passed as strings, regardless of what types they may represent. If you pass "10" on the command line, you are actually passing the character array
{ '1', '0', '\0' }
not the integer 10.
If the parameter you want consists of a single character, you can always just take the first character:
char timer_unit = argv[2][0];
If you only ever want the first character from the parameter the folowing will extract it from string:
char timer_unit = argv[2][0];
The issue is that argv[2] is a char* (C-string) not char.
You are probably not passing in what you think (though this should come from the command line). Please show the complete error message and code, but it looks like you need to deal with the second argument as char *argv[], instead of char argv[] -- that is, as a list of character arrays, as opposed to a single character array.
Everything stays strings when you pass them in to your program as arguments, even if they are single characters. For example, if your program was called "myprog" and you had this at the command line:
myprog arg1 53 c a "hey there!"
Then what you get in the program is the following:
printf("%d\n", argc);
for(int i = 0; i < argc; i++)
{
printf("%s\n", argv[0]);
}
The output of that would be:
6
myprog
arg1
53
c
a
hey there!
The point being that everything on the command line turns into null-terminated strings, even single characters. If you wanted to get the char 'c' from the command line, you'd need to do this:
char value = argv[3][0];
not
char value = argv[3]; // Error!
Even the value of "53" doesn't turn into an int. you can't do:
int number = argv[2]; // Error!
argv[2] is { '5', '2', '\0' }. You have to do this:
int number = atoi(argv[2]); // Converts from a string to an int
I hope this is clear.
Edit: btw, everything above is just as valid for C (hence the printf statements). It works EXACTLY the same in C++.