I'm working with a simple fopen, fwrite, fflush, fclose body of code. For some reason, however, every time I try to create a FILE * object, it crashes. My code is below.
//fopen
FILE * f_data = fopen("out.txt", 'wb'); // BREAKS HERE
if (f_data == NULL) { printf("fopen failed!"); }
//fwrite
int fwritten = fwrite(data, 1, content_length, f_data);
if (fwritten == 0) { printf("fwrite failed!"); }
//fflush
int flush = fflush(f_data);
if (flush != 0) { printf("fflush failed!"); }
//fclose
int close = fclose(f_data);
if (close != 0) { printf("fclose failed!"); }
Whenever I run this code, I get the following error:
Unhandled exception at 0x5F52C795 (ucrtbased.dll) in main.exe: 0xC0000005: Access violation reading location 0x00007762.
I've been researching this problem for about an hour now, to no avail. I've learned that this is Windows telling me I've encountered a segmentation fault, possibly from trying to dereference a NULL pointer.
If anybody has some insight on why my File * instantiation won't work, please share!
EDIT: I'm not sure it's relevant to this question but the data buffer being written is a simple string: "Hello, world, and all who inhabit it!" and content_length is set to sizeof(data).
Related
Goodday all,
I'm getting the following error:
First-chance exception at 0x67887AB7 (SDL2_mixer.dll) in Racing.exe: 0xC0000005: Access violation reading location 0xCCCCCCD4.
I think the problem could be with the pointer, but I'm not experienced enough in c++ to find it.
I'm hoping someone can tell me what I did wrong, and hopefully I can learn from it :)
Trying to call it from my gamebus.
Music Mus;
Mus.SpeelGeluid("crash");
Music class
bool Music::LoadMusic(){
//Load music
Mix_Music *gMusic = NULL;
gMusic = Mix_LoadMUS("MusicTest.wav");
Mix_PlayMusic(gMusic, -1);
bool success = true;
if (gMusic == NULL)
{
printf("Failed to load Music background song! SDL_mixer Error: %s\n", Mix_GetError());
success = false;
}
// Load sound effects
Mix_Chunk *gCrash = NULL;
gCrash = Mix_LoadWAV("Crash.wav");
if (gCrash == NULL)
{
printf("Failed to load scratch sound effect! SDL_mixer Error: %s\n", Mix_GetError());
success = false;
}
return success;
}
void Music::SpeelGeluid(string soundname){
cout << soundname << endl;
if (soundname == "crash")
{
try
{
Mix_PlayChannel(-1, gCrash, 0);
}
catch (int e)
{
cout << "An exception occurred. Exception Nr. " << e << '\n';
}
}
else
{
} }
Thank you for your time
You have two major problems:
First, you're using gMusic before checking whether it's NULL.
This may crash Mix_PlayMusic, and actually means that compilers may optimise out the later NULL check.
Second, and most likely the cause of your problem, you're declaring gCrash and gMusic as local variables in LoadMusic.
From the names, and your use of gCrash in SpeelGeluid, my educated guess is that you also have two global variables, or possibly member variables, with the same names where you intend to store the results of loading the files.
Your local variables are hiding these globals, and you're only modifying the local variables.
Remove the lines
Mix_Music *gMusic = NULL;
and
Mix_Chunk *gCrash = NULL;
to get rid of these local variables.
And do initialise the globals to NULL when you define them.
Check your pointers as soon as you've allocated them and handle them appropriately. You nearly do:
gMusic = Mix_LoadMUS("MusicTest.wav");
Mix_PlayMusic(gMusic, -1); // <- You're using the pointer here before you check it
bool success = true;
if (gMusic == NULL) // <- this needs to be immediately after assignment
That's just from the code you've pointed. It's also possible you've missed a generic initialisation call from the SDL2_mixer.dll.
Do debug it and step through line by line so you know which bit is causing the error.
I have a problem when running a testcase in debug-mode: I get a pop-up-box with the message "Unhandled exception at 0x7c812fd3 in Test.exe: 0xE0000003: 0xe0000003.". The code breaks in free.c:
void __cdecl _free_base (void * pBlock)
{
int retval = 0;
if (pBlock == NULL)
return;
RTCCALLBACK(_RTC_Free_hook, (pBlock, 0));
retval = HeapFree(_crtheap, 0, pBlock);
if (retval == 0)
{
errno = _get_errno_from_oserr(GetLastError());
}
}
at line "retval =..." with _crtheap = 0x00df0000 and pBlock = 0x967c93d3. The call stack breaks at "kernel32.dll!7c812fd3() " and another entry further down in the call stack:
">msvcr100d.dll!_free_base(void * pBlock=0x967c93d3) Line 50 + 0x13 bytes".
I have googled quite a bit and the problem might come from freeing memory severel times.
Despite this vague and messy description can anyone hint how to locate the problem ? and maybe how to fix it ?
What strikes me a bit odd is that I do not experience this when running the test in release-mode...
Kind regards,
Svend
Have you tried to run these testcases under visual studio debugger?
Debugger should catch this exception and you can verify call stack and locate where issue is.
I already do know, that it is impossible to simply detect if socket is disconnected or not - the server and clients must shout "Can you hear me?" and "Yeah I can." just like we do on skype.
But when boost::asio socket is disconnected from other side I obtain Unhanded exception when trying to read from socket. This is kind of disconnect detection useful enough for me. Can I handle that exception, so instead of crashing, the program will produce message in the console?
Some code for those who need it for everything:
bool SocketClient::read(int bytes, char *text) {
char buffer = 0;
int length = 0;
while(bytes>0) {
size_t len = sock.receive(boost::asio::buffer(&buffer, 1)); //boom: UNHANDLED EXCEPTION
bytes--;
text[length] = buffer;
length++;
}
return true;
}
Because I am connecting to minecraft server, I know when the client is disconnected - exception is caused on any read/write attempt.
try
{
size_t len = sock.receive(boost::asio::buffer(&buffer, 1)); //boom: UNHANDLED EXCEPTION
// More code ...
}
catch (const boost::system::system_error& ex)
{
if ( ex.code() == boost::asio::error::eof )
{
// Work your magic (console logging, retry , bailout etc.)
}
}
Please also take a look at the doc. In the worst case , you could infer the exception type from the debugger :)
Error at line "luaL_dofile" and debugger doesn't show anything about error.
I can use command "luaL_dostring" but I don't know why I can't dofile.
My code is following:
const char* file = "/app_home/data/minigames/mg_hint_machine_2.lua";
ret = luaL_dofile(LS, file);
if(ret != 0){
PRINTF("Error occurs when calling luaL_dofile() Hint Machine 0x%x\n",ret);
}
else PRINT("\nDOFILE SUCCESS");
and debugger shows error in this line and "ret" still not get returned value from dofile.
If you want to see about error in debugger
02C2D304 7C21016A stdux r1,r1,r0 03 (02C2D300) REG PIPE LSU
Debugger points in this line and I can't understand it.
As an elaboration on superzilla's answer (upvote that answer rather than this one),
to get the error message your code needs to look like this:
const char* file = "/app_home/data/minigames/mg_hint_machine_2.lua";
ret = luaL_dofile(LS, file);
if(ret != 0){
PRINTF("Error occurs when calling luaL_dofile() Hint Machine 0x%x\n",ret);
PRINTF("Error: %s", lua_tostring(LS,-1));
}
else PRINT("\nDOFILE SUCCESS");
Your change (in the comments) changed the luaL_dofile to a luaL_dostring, which is why you're getting unexpected error message ( as mentioned here ).
Putting this in the body of your if statement will help us narrow down the problem:
printf("%s\\n",lua_tostring(LS,-1));
It'll tell us what Lua is reporting when it crashes.
getting this error in an application written in C++ (VS 2010):
Unhandled exception at 0x77648da9 in divt.exe: 0xC0000005: Access
violation writing location 0x00000014.
it points to this function in free.c:
void __cdecl _free_base (void * pBlock)
{
int retval = 0;
if (pBlock == NULL)
return;
RTCCALLBACK(_RTC_Free_hook, (pBlock, 0));
retval = HeapFree(_crtheap, 0, pBlock);
if (retval == 0) //<-----------------------right here
{
errno = _get_errno_from_oserr(GetLastError());
}
}
Via debugging I was able to determine where its actually crashing:
void MenuState::LoadContentFromFile(char* File,std::string &Content)
{
std::string strbuf;
char buffer[1028];
std::fstream file;
file.open(File,std::ios_base::in);
if(file.fail())
{
Content = ErrorTable->GetString("W0001");
return;
}
if(file.is_open())
{
while(!file.eof())
{
file.getline(buffer,128,'\n'); // <----here
strbuf = buffer;
Content += strbuf + "\n";
}
}
file.close();
strbuf.clear();
}
It crashes on file.getline(buffer,128,'\n');
I don't understand why but it's only doing it in release build (Optimizations turned off), on debug build its working fine.
Any Ideas?
I know this is an old question, but when you encounter these sorts of issues buried deep in files such as, free.c or xmemory, you may also want to double check your project configuration. Especially when the issue pertains to only certain build configurations.
For example, in MSVC check your Project Properties > Configuration Properties > C/C++ > Code Generation > Runtime Library. Make sure it consistent for all dependencies and that it is set to a Debug/Release variant depending on the current build.
I would bet that the read prior to the read crashing the application actually failed (although I'm not quite sure why it would crash). The important thing to note is that eof() is only good for determining what caused a read failure (and typically suppressing an error message). In addition, you always want to check after the read whether it was successful. Finally, I can't see any reason why you don't read an std::string directly. In summary, try to use this loop instead:
for (std::string strbuf; std::getline(file, strbuf); ) {
Content += strbuf;
}
Asked a friend for help, we came up with this Solution:
std::string strbuf;
char buffer[256] = "\0";
FILE* f = fopen(File, "rt");
while(fgets(buffer,sizeof(buffer),f) != NULL)
{
Content += buffer;
}
fclose(f);
strbuf.clear();
Works fine, still thanks for your efforts.