I've spent many hours on here looking for help on what is apparently a common error but none that I've seen seems to fit my case.
I am migrating a old out sourced program that was written in Visual Studio 6 C++ to Visual Studio 2012 and fortunately for me as I'm not a C++ programmer (just a lowly VB and C# developer). The migration wizard and the internet have been a great help in helping me find and correct code that the wizard can't handle.
In this code block which I believe is doing nothing more than creating a directory
int CreateAllDirectories(const char* pszDir)
{
char* pszLastSlash;
char cTmp;
if( _access( pszDir, 0 ) != -1 ) {
// it already exists
return 0;
}
pszLastSlash = strrchr( pszDir, '\\' );
if ( pszLastSlash ) {
cTmp = *pszLastSlash;
*pszLastSlash = '\0';
// try again with one less dir
CreateAllDirectories( pszDir );
*pszLastSlash = cTmp;
}
if ( _mkdir( pszDir ) == -1 ) {
return -1;
}
return 0;
}
an error generates when the results of strrchr( pszDir, '\' ) are assigned to the variable pszLastSlash. From the rest of this code it looks like pszLastSlash = strrchr( pszDir, '\' ); is a valid expression.
Is the issue with the double backslash which to me looks like and escape sequence.
Maybe in this line...
pszLastSlash = strrchr( pszDir, '\\' );
pszLastSlash is not constant but pszDir is constant. There are two defs for strrchr() (see http://www.cplusplus.com/reference/cstring/strchr/)...
const char * strchr ( const char * str, int character );
char * strchr ( char * str, int character );
Because you input a constant char *, it will try to use the def that returns a const char*, but you're assigning it to a non-const char*. I think that is what is generating your error.
Because pszDir is const, the pointer returned to you is const because you shouldn't be modifying the area of memory pointed to by pszDir.
If you have allocated pszDir yourself, and you know it is safe to modify, your could relax your const contraint in the function def? I.e.,
int CreateAllDirectories(char* pszDir)
But, only do this is pszDir is a string that you own and can modify :)
I just noticed in the C++ reference page that...
In C, this function is only declared as:
char * strchr ( const char *, int );
So, if you previously used C, then that would explain why you see the error now.
Since this line
*pszLastSlash = '\0';
is modifying the buffer passed into your function, you must not promise your caller that you won't modify the buffer. Therefore
int CreateAllDirectories(char* pszDir);
is the correct signature
You can try putting new in the middle of
pszLastSlash = strrchr( pszDir, '\' );
So, it will be
:pszLastSlash = new strrchr( pszDir, '\' );
Related
This code compiles perfect:
if ( args.Length() > 0 ) {
if ( args[0]->IsString() ) {
String::Utf8Value szQMN( args[0]->ToString() ) ;
printf( "(cc)>>>> qmn is [%s].\n", (const char*)(* szQMN) ) ;
} ;
} ;
But this one does not :
if ( args.Length() > 0 ) {
if ( args[0]->IsString() ) {
String::Utf8Value szQMN( args[0]->ToString() ) ; // <<<< (A)
} ;
} ;
printf( "(cc)>>>> qmn is [%s].\n", (const char*)(* szQMN) ) ; // <<<< (B)
Error says : "error C2065: 'szQMN' : undeclared identifier" on line (B)
This means to me that the sentence marked (A) is a definition at the same time as an assignement, right ?
And compiler decides it is "conditionally" defined as it is within two "IF's" ?
My question is : how to move the declaration out of the two "IF's" ?
In this way I also can give it a defalut value ... in case a IF fails.
If I write this line out of the two "IF's"
String::Utf8Value szQMN ("") ;
... then I get the error :
cannot convert argument 1 from 'const char [1]' to 'v8::Handle<v8::Value>'
Any ideas?
This means to me that the sentence marked (A) is a definition at the same time as an assignement, right?
Technically it is a constructor call that creates a variable and initializes it.
Also note that automatic variables exist only until the end of the scope (usually a block inside {} brackets). That is why your second code example does not compile.
if (condition)
{
int x = 5;
}
x = 6; // error, x does not exist anymore
My question is : how to move the declaration out of the two "IF's"?
String::Utf8Value szQMN ("");
This is a constructor call of the class String::Utf8Value class. From the error message it takes a parameter of type v8::Handle<v8::Value>. Without knowing what this is I cannot give you an answer how to call it. You wanted to pass "" which is of type const char* or const char[1] and the compiler is telling you that it does not take that parameter.
Edit:
From the link that DeepBlackDwarf provided in the comment, this is how you create a Utf8Value from a string:
std::string something("hello world");
Handle<Value> something_else = String::New( something.c_str() );
So in your case you would do:
String::Utf8Value szQMN (String::New(""));
the definition in the IF's loop is only works in this loop.
So in the (B) sentence,the definition has already been expired.
If you need to use the var both in the IF's loop and outside,you can declare a global variability by this sentence :
extern String::Utf8Value szQMN( args[0]->ToString() ) ;
I am trying to store some contents into a string variable by passing it as a parameter in various types of Windows API functions which accepts variable like char *.
For example, my code is:-
std::string myString;
GetCurrentDirectoryA( MAX_PATH, myString );
Now how do I convert the string variable to LPSTR in this case.
Please see, this function is not meant for passing the contents of string as input, but the function stores some contents into string variable after execution. So, myString.c_str( ) is ruled out.
Edit: I have a workaround solution of removing the concept of string and replacing it with something like
char myString[ MAX_PATH ];
but that is not my objective. I want to make use of string. Is there any way possible?
Also casting like
GetCurrentDirectoryA( MAX_PATH, ( LPSTR ) myString );
is not working.
Thanks in advance for the help.
Usually, people rewrite the Windows functions they need to be std::string friendly, like this:
std::string GetCurrentDirectoryA()
{
char buffer[MAX_PATH];
GetCurrentDirectoryA( MAX_PATH, buffer );
return std::string(buffer);
}
or this for wide char support:
std::wstring GetCurrentDirectoryW()
{
wchar_t buffer[MAX_PATH];
GetCurrentDirectoryW( MAX_PATH, buffer );
return std::wstring(buffer);
}
LPTSTR is defined as TCHAR*, so actually it is just an ordinary C-string, BUT it depends on whether you are working with ASCII or with Unicode in your code. So do
LPTSTR lpStr = new TCHAR[256];
ZeroMemory(lpStr, 256);
//fill the string using i.e. _tcscpy
const char* cpy = myString.c_str();
_tcscpy (lpStr, cpy);
//use lpStr
See here for a reference on _tcscpy and this thread.
Typically, I would read the data into a TCHAR and then copy it into my std::string. That's the simplest way.
I've never done any C++/COM work before, so I'm trying to hijack an existing solution and just alter it to my needs. The project was written and successfully compiled with VC 6 and I'm attempting to work with it now in 2010. I had to change a few references to get it to compile, but for some reason, the dll I generate is causing an exception on my system (the original works fine). Doing some research on the error, it looks like I'm getting a buffer overflow when I try to declare a char array.
bool CFile::simpleWrite(char* cData)
{
try{
// temp result variable
BOOL bResult = 0;
// file handle
HANDLE hFile = INVALID_HANDLE_VALUE;
// get the CMain singleton
CMain* m_pMain = CMain::GetInstance();
// this point gets synchronization to ensure we get unique file name...
char cDirFilename[MAX_PATH + 1];
GetLogFileName(cDirFilename, MAX_PATH);
// sanity check
if(strcmp(cDirFilename, "c:\\") == 0) assert(0);
// try and create a file
hFile = CreateFile( cDirFilename, GENERIC_WRITE, FILE_SHARE_READ,NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL );
// if have a good file handle
if(hFile != INVALID_HANDLE_VALUE){
size_t lenFileData = strlen(cData) + 72;
char* cFileData = new char[lenFileData];
_snprintf(cFileData, lenFileData, "<?xml version=\"1.0\"?>\r\n<RootElement>\r\n%s</RootElement>\r\n\0", cData);
...
Here is the declaration/assignment for cData (cXML in the calling method).
char cXML[EVENT_LOG_MAX_MESSAGE];
// get the CMain singleton
CMain* pMain = CMain::GetInstance();
long lThreadID = GetCurrentThreadId();
// put the parameters into XML format
pMain->BuildXML(cXML, EVENT_LOG_MAX_MESSAGE,errLogLevel,userActivityID,methodName,lineNumber,className,AppID,errorDescription,errorID,lThreadID);
// write the data to file
if(!simpleWrite(cXML))
...
BuildXML is doing a _snprintf into cXML and returning it.
Here is the stacktrace going from my call into some of the VC files.
Test.dll!_heap_alloc_base(unsigned int size) Line 55 C
Test.dll!_heap_alloc_dbg_impl(unsigned int nSize, int nBlockUse, const char * szFileName, int nLine, int * errno_tmp) Line 431 + 0x9 bytes C++
Test.dll!_nh_malloc_dbg_impl(unsigned int nSize, int nhFlag, int nBlockUse, const char * szFileName, int nLine, int * errno_tmp) Line 239 + 0x19 bytes C++
Test.dll!_nh_malloc_dbg(unsigned int nSize, int nhFlag, int nBlockUse, const char * szFileName, int nLine) Line 302 + 0x1d bytes C++
Test.dll!malloc(unsigned int nSize) Line 56 + 0x15 bytes C++
Test.dll!operator new(unsigned int size) Line 59 + 0x9 bytes C++
Test.dll!operator new[](unsigned int count) Line 6 + 0x9 bytes C++
Test.dll!CFile::simpleWrite(char * cData) Line 87 + 0xc bytes C++
I'm sure there is some stupid basic mistake, but I can't seem to get it figured out.
Your error is most likely somewhere else where you end up corrupting the heap. I notice you use strlen here without adding one for the terminating zero. Have a look in your code to see if you use strlen for allocating memory and copying somewhere, because I think you're corrupting the heap by allocating one byte too little and then strcpy'ing to it.
As I suspected, this was all my own stupidity. This COM application had a dependency that I wasn't aware of. Never saw anything trying to look for it in the process monitor and the project had a local copy of the file for compile purposes apparently. Thanks for the input though.
I'm pretty new to C, and trying to write a function that will parse a string such as:
"This (5 spaces here) is (1 space
here) a (2 spaces here) string."
The function header would have a pointer to the string passed in such as:
bool Class::Parse( unsigned char* string )
In the end I'd like to parse each word regardless of the number of spaces between words, and store the words in a dynamic array.
Forgive the silly questions...
But what would be the most efficient way to do this if I am iterating over each character? Is that how strings are stored? So if I was to start iterating with:
while ( (*string) != '\0' ) {
--print *string here--
}
Would that be printing out
T
h
i... etc?
Thank you very much for any help you can provide.
from http://www.cplusplus.com/reference/clibrary/cstring/strtok/
/* strtok example */
#include <stdio.h>
#include <string.h>
int main ()
{
char str[] ="- This, a sample string.";
char * pch;
printf ("Splitting string \"%s\" into tokens:\n",str);
pch = strtok (str," ,.-"); /* split the string on these delimiters into "tokens" */
while (pch != NULL)
{
printf ("%s\n",pch);
pch = strtok (NULL, " ,.-"); /* split the string on these delimiters into "tokens" */
}
return 0;
}
Splitting string "- This, a sample string." into tokens:
This
a
sample
string
First of all, C does not have classes, so in a C program you would probably define your function with a prototype more like one of the following:
char ** my_prog_parse(char * string) {
/* (returns a malloc'd array of pointers into the original string, which has had
* \0 added throughout ) */
char ** my_prog_parse(const char * string) {
/* (returns a malloc'd NULL-terminated array of pointers to malloc'd strings) */
void my_prog_parse(const char * string, char buf, size_t bufsiz,
char ** strings, size_t nstrings)
/* builds a NULL-terminated array of pointers into buf, all memory
provided by caller) */
However, it is perfectly possible to use C-style strings in C++...
You could write your loop as
while (*string) { ... ; string++; }
and it will compile to exactly the same assembler on a modern optimizing compiler. yes, that is a correct way to iterate through a C-style string.
Take a look at the functions strtok, strchr, strstr, and strspn... one of them may help you build a solution.
I wouldn't do any non-trivial parsing in C, it's too laborious, the language is not suitable for that. But if you mean C++, and it looks like you do, since you wrote Class::Parse, then writing recursive descent parsers is pretty easy, and you don't need to reinvent the wheel. You can take Spirit for example, or AXE, if you compiler supports C++0x. For example, your parser in AXE can be written in few lines:
// assuming you have 0-terminated string
bool Class::Parse(const char* str)
{
auto space = r_lit(' ');
auto string_rule = "This" & r_many(space, 5) & space & 'a' & r_many(space, 2)
& "string" & r_end();
return string_rule(str, str + strlen(str)).matched;
}
I want to send the double quote character to my CreateProcess function. How can I do the correct way? I want to send all of this characters: "%h"
CreateProcess(L"C:\\identify -format ",L"\"%h\" trustedsnapshot.png",0,0,TRUE,NORMAL_PRIORITY_CLASS|CREATE_NO_WINDOW,0,0,&sInfo,&pInfo);
note: "identify" is an Imagemagick program.
Here is the full code:
int ExecuteExternalFile()
{
SECURITY_ATTRIBUTES secattr;
ZeroMemory(&secattr,sizeof(secattr));
secattr.nLength = sizeof(secattr);
secattr.bInheritHandle = TRUE;
HANDLE rPipe, wPipe;
//Create pipes to write and read data
CreatePipe(&rPipe,&wPipe,&secattr,0);
STARTUPINFO sInfo;
ZeroMemory(&sInfo,sizeof(sInfo));
PROCESS_INFORMATION pInfo;
ZeroMemory(&pInfo,sizeof(pInfo));
sInfo.cb=sizeof(sInfo);
sInfo.dwFlags=STARTF_USESTDHANDLES;
sInfo.hStdInput=NULL;
sInfo.hStdOutput=wPipe;
sInfo.hStdError=wPipe;
CreateProcess(L"C:\\identify",L" -format \"%h\" trustedsnapshot.png",0,0,TRUE,NORMAL_PRIORITY_CLASS|CREATE_NO_WINDOW,0,0,&sInfo,&pInfo);
CloseHandle(wPipe);
char buf[100];
DWORD reDword;
CString m_csOutput,csTemp;
BOOL res;
do
{
res=::ReadFile(rPipe,buf,100,&reDword,0);
csTemp=buf;
m_csOutput+=csTemp.Left(reDword);
}while(res);
//return m_csOutput;
float fvar;
//fvar = atof((const char *)(LPCTSTR)(m_csOutput)); ori
//fvar=atof((LPCTSTR)m_csOutput);
fvar = _tstof(m_csOutput);
const size_t len = 256;
wchar_t buffer[len] = {};
_snwprintf(buffer, len - 1, L"%d", fvar);
MessageBox(NULL, buffer, L"test print createprocess value", MB_OK);
return fvar;
}
I need this function to return the integer value from the CreateProcess.
The way you wrote it should work OK, or do you have any problems with it?
Your problem is not the quotes. There are two problems with the way you pass parameters to CreateProcess. The first is that the command line passed in the second argument should include the name of the command (that is, it should include the value for "argv[0]"), the second is that the redirection (> testt.txt) is not handled by the CreateProcess API,. Unless c:\identify expects such arguemnts, you should not include this in the command line.