• 0

Quick query regarding pointer to struct and heapalloc in C++...


Question

Got a quick C++ question here, tl;dr version is: Got a struct with some objects, creating a new array of objects, using heapalloc (which I thought would be similar to initialising them all manually, I can access/change VarB and VarC but whatever I try to do with VarA causes exception nightmare)

Long version: I've got a struct;

typedef struct ThreadSocketData
{
	list<SOCKET*> VarA;
	unsigned int VarB;
	unsigned int VarC;
} THREADSOCKETDATA, *PTHREADSOCKETDATA;

I'm allocating it as a global and in a function as;

PTHREADSOCKETDATA *pDataArrays;
...
pDataArrays = new PTHREADSOCKETDATA[2];
...
pDataArrays[i] = (PTHREADSOCKETDATA)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(THREADSOCKETDATA));

Then I try to use it like so;

pDataArrays[1]->VarB = 5;
cout << pDataArrays[1]->VarB << endl; //works fine
SOCKET *ASocket = new SOCKET;
*ASocket = 5;
pDataArrays[0]->VarA.push_back(ASocket); //exception crazy

I've tried created it alternatively and like so and it seems to work fine;

pDataArrays = new PTHREADSOCKETDATA[2];
pDataArrays[0] = new THREADSOCKETDATA;
pDataArrays[1] = new THREADSOCKETDATA;
pDataArrays[0]->VarC = 5;
pDataArrays[0]->VarB = 4;
pDataArrays[0]->VarA.begin();
SOCKET *ASocket = new SOCKET;
*ASocket = 18;
pDataArrays[0]->VarA.push_back(ASocket);

So why does the second way work but the first doesn't fully work? Surely using heapalloc would have the same effect as manually allocating it all?

10 answers to this question

Recommended Posts

  • 0

Operator new calls constructors, malloc/HeapAlloc don't. My guess is that in your first example, VarA is uninitialized because its constructor hasn't run, so you cannot use it.

This would all be moot if you were using C++ idioms rather than mixing C idioms in there. In C++ you use new and delete, not malloc, unless you're implementing an allocator or something. Actually, scratch that, in modern C++ you don't even write new and delete, you use smart pointers and containers (see for instance http://fr.slideshare.net/sermp/without-new-and-delete ). In your example if you replace all the C-style arrays with std::vector, and all the raw pointers with smart pointers, every constructor and destructor is guaranteed to run exactly when it should and you shouldn't be leaking anything or accessing uninitialized state.

Also, as a matter of style you don't need to write typedef struct MyType {} MYTYPE in C++, just struct MYTYPE {}, and you'd probably want to avoid SCREAMINGCAPS for all your type names if you don't want your code to look like 9-year olds having an internet argument.

  • 0

This is my first program with threading (not done it before) so I've been modifying the sample MSDN code which had it all in caps, not my idea of naming but good idea, I'll change that.

I don't think I can use smart pointers for this though? The pDataArray {i} is sent by reference to thread {i} although I want to be able to manipulate it from within the main thread therefore I left the heapalloc code as it was provided by MS, so if I remove all the heapalloc/heapfree and just use normal new/delete and pass that in CreateThread() it will work?

  • 0
  On 28/10/2015 at 21:08, Andre S. said:

Do you really need to use the Win32 function CreateThread rather than standard C++ threads

Well the problem is I'm making this program across 3 different types of PCs, my home PC has visual studio 2015 so std::thread is fine, I already use it to get the number of CPUs, another has visual studio 2013 and I'm not sure if it fully has std::thread or only parts of it? And the other has visual studio 2010, which doesn't have any std::thread support at all :(.

Using std::thread I can then pass it smart pointers or references to objects I manually new/delete and access them from the thread and main program? Also is there a std:: replacement for Createevent/Resetevent/Setevent/Waitformultipleobjects?

  • 0

VS2015 Community Edition is free ;)

Yes you can pass any object to an std::thread, look at the documentation. For a ManualResetEvent or AutoResetEvent you could implement that pretty straightforwardly with std::condition_variable and std::mutex, there are examples online.

 

  • 0
  On 28/10/2015 at 21:24, n_K said:

Well the problem is I'm making this program across 3 different types of PCs, my home PC has visual studio 2015 so std::thread is fine, I already use it to get the number of CPUs, another has visual studio 2013 and I'm not sure if it fully has std::thread or only parts of it? And the other has visual studio 2010, which doesn't have any std::thread support at all :(.

Using std::thread I can then pass it smart pointers or references to objects I manually new/delete and access them from the thread and main program? Also is there a std:: replacement for Createevent/Resetevent/Setevent/Waitformultipleobjects?

Like everyone says - VS2015 freebie - no need to be complicated

But you never said what sort of code you are making. If it's anything connected with Device drivers then the std stuff is out the window...

  • 0

I've got VS 2015 community on this pc which is fine - it's my PC. The other two PCs are not mine, they're in an educational establishment, I'm not administrator so I can't just install VS 2015 on them and why I have to put up with using 2010 and 2013 also.

I'll see if I can get a portable mingw working on the other PCs and see what happens if I chuck the code at that instead of using 2010 and 2013!

Nope not drivers, just testing out threads and winsock and the like. I've not looked into drivers, can MS drivers use multiple threads (even if not using std::thread threads)? Can Linux modules use threads (using std::thread)?

Thanks!

  • 0

It's a bad idea to mix allocation techniques like that unless you know what you're doing and it's for a good reason. In particular, STL data structures (such as list) only get initialised properly if you use the built-in new() operator to allocate them.

You might be able to get around it by calling new() on VarA after allocating the structure with malloc().

static const int ARRAY_SIZE = 20
THREADSOCKETDATA* myArray = malloc(ARRAY_SIZE * sizeof(THREADSOCKETDATA));

for (int i = 0; i < ARRAY_SIZE; i++)
    myArray[i].VarA = new list<SOCKET*>;
    
// clean up    
free(myArray);

I wouldn't recommend it though.

For efficiency purposes, I'd also allocate the entire array as a contiguous block of memory, rather than making multiple heap allocations for each individual structure.

  • 0
  On 29/10/2015 at 15:39, n_K said:

I've got VS 2015 community on this pc which is fine - it's my PC. The other two PCs are not mine, they're in an educational establishment, I'm not administrator so I can't just install VS 2015 on them and why I have to put up with using 2010 and 2013 also.

I'll see if I can get a portable mingw working on the other PCs and see what happens if I chuck the code at that instead of using 2010 and 2013!

Nope not drivers, just testing out threads and winsock and the like. I've not looked into drivers, can MS drivers use multiple threads (even if not using std::thread threads)? Can Linux modules use threads (using std::thread)?

Thanks!

Threads are easy to make. After that it can get interesting. There is a reason why just about every GUI system is limited to single-threaded.

If you are doing a real device driver for hardware then you have interrupts in which you need to store whatever you need within 30 millisecs and then Queue up worker threads to do the real processing which are also time limited so you then can have long running threads to process stuff as a background service. You need to be very aware of which variables are atomic and which data structures can get clobbered by your interrupt code, your DPC code, your worker thread etc. The killer is multi-core because it's so fast. It can look like impossible things happen like only 1/2 of a store to memory etc but then it turns out that compiler operation wasn't atomic...

The solution most people use is locks. After you do some device driver stuff, you learn to strike a more delicate balance. So learn what's atomic and every O/S has O/S API calls for safe atomic updates I think.

This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Posts

    • Camtasia screen recorder now has a free version that works in your browser by Aditya Tiwari TechSmith, the minds behind Camtasia, has announced an online version of its popular screen recording and video editing tool. The web-based version, called Camtasia Online, is now available through popular web browsers like Google Chrome and Safari. Camtasia Online is essentially a stripped-down version of its desktop counterpart. It is designed to let you screen record, customize, share, and collaborate on high-quality videos without needing to download any software or purchase a subscription. Screen recording tools are often used to create step-by-step walkthroughs and tutorials, personalized feedback or coaching, and showcase a product or service. Camtasia has been around since 2002 and is primarily accessible through paid offerings. The screen recorder has over 34 million users globally. TechSmith offers a free trial of the desktop version, but the exported files automatically include a watermark. That's not the case with its modern counterpart, according to the company, which doesn't require any subscription. Note that while the online screen recorder is free to use, you still need a TechSmith account to use it. "While this first release focuses on streamlined creation, it will continue to grow in capability, and users can move projects into the Camtasia desktop editor for more advanced editing when needed,” TechSmith's CTO, Tony Lambert, said in an emailed statement. The web-based version allows you to create 1080p short clips (Scenes) of up to 5 minutes in length, with options to record a specific app, window, or the entire screen. It can record the screen, camera, and microphone on separate layers for more flexibility during editing. You can record multiple scenes and export them as a single video file. Camtasia Online offers a variety of visual effects and backgrounds, and the ability to pick a custom size and position on the screen. For instance, you can place the screen recording in the top-left or bottom-right corner of the screen, depending on your preference. Camtasia Online comes with more than 85 pre-defined "looks" to match your preference, its maker said. You can remove the background, add borders, drop shadows, make corners round, add reflections, and more, before and after recording a scene. You can also trim a video after recording with support for reversible changes. The online screen recorder also lets you collaborate with other users by sending invitation links. You can either give them access to the entire project or just a single scene. You can also preview the scenes before exporting them or re-record if something doesn't feel right. TechSmith also offers integration with Camtasia 2025's desktop version, allowing you to utilize additional features such as transitions, annotations, and dynamic captions. You can click on the Export button to download the project and use it in the desktop editor. Overall, Camtasia Online could be a suitable option for quick screen recording sessions and a viable choice for beginners. However, one downside is that it can be a bit tricky to download the video file directly through your browser. First, click on the "Export to Screencast" option in Export settings, which opens TechSmith's online hosting service. Then, make sure you're signed in to your TechSmith account, and click on More > Download to download the video file to your device.
    • Intel is pretty consistent about dropping a new CPU every year, typically in Q3. The fact that we are starting to get more information now implies they are on track.
    • TerraMaster D4 SSD review: Palm-sized DAS with up to 32TB of storage over USB4 by Steven Parker TerraMaster is back with another disk enclosure. I was offered the chance to take a look at their new D4 SSD, which is a palm-sized DAS that supports four M.2 SSDs ahead of its launch, today, on June 17. This follows our review of the all SATA D9-320 that we did last month, and the D5 Hybrid and D8 Hybrid, both of which are essentially multi-disk (HDD and SSD) enclosures for external backup, or to expand the capacity of a NAS. Here are the full specs of it: TerraMaster D4 SSD Dimensions: 138 x 60 x 140 mm Weight: 419g (with 3x M.2 SSDs) Power: 24W (100V to 240V AC) 50/60 HZ, Single Frequency System Fan: 50 x 50 x 10mm x3 Max Noise Level: 19 dB(A) using M.2 SSDs in standby mode; Test environment noise: 17.3dB(A); Test distance: 1m Compatible Disk Types: PCIe NVMe M.2 2280 SSD Reading Speed (max.) Writing Speed (max.) 3257 MB/s (Samsung 990 Pro 4TB x4 RAID0; 1600MB/s 4TB x1 3192 MB/s (Samsung 990 Pro 4TB x4 RAID0; 1500MB/s 4TB x1 Power Consumption: 15.0 W (Fully loaded Seagate 2TB M.2 SSDs in read/write state) 6.0 W (Fully loaded Seagate 2TB M.2 SSDs in hibernation) Raw Capacity: 32TB (8TB SSD x4) RAIDs Supported: SINGLE DISK Power saving: Hibernation Ports: USB4 40Gbps DC IN 12V Barrelport (MSRP) Price: $299.99 First, I should mention that TerraMaster only put SINGLE DISK support in the RAID specification, however unlike the D9-320 9-bay HDD enclosure, I was surprised to see that it actually supports both Striped and Spanned volumes in Windows 11, so you can get RAID1 in Windows 11 with this if you wanted, or simply combine all of the available drives into a single volume spanning the size of all drives combined. Technically, they are correct with the only SINGLE disk support, that is, if you plan to connect it to a NAS. Because it connects over USB, this means you will only be able to create usbshares, not storage pools. However, it is a nice surprise that Windows supports more functions with this D4 SSD than a NAS offers, which may also result in how you decide to use it. Also, for some reason, they have put that it weighs 600 grams. I think this is the package weight, because I weighed the D4 SSD after putting in three SSDs, and it came to 419 grams, which is really light! What's in the box D4 SSD device USB Type-C cable (C to C) 0.8m Power adapter Quick installation guide Limited warranty notice Bag of 2x M.2 screws I should mention that the "Quick Installation Guide" is simply a card with a QR code that links to https://start.terra-master.com. It requests your email and product details, which then opens to a full online User Guide. After getting to the end of the online User Guide (37 pages), which frustratingly encountered really slow page loads at times, there's a link to download a PDF of the User Manual. Design The design of the D4 SSD matches that of the F8 SSD Plus that I reviewed last year; in fact, it shares almost the same dimensions, but is 3.7cm shorter than its full NAS SSD counterpart, which is another example of how TerraMaster disk enclosures closely match their NAS sibling. It is essentially a metal frame with what I would call a matte black plastic cover. It is a bit of a dust and fingerprint magnet, too, but a quick wipe, and it's all gone, unlike what you would see with a glossy plastic exterior. It has a slightly textured feel to it and definitely feels premium, but also not in such a way that it would easily slip out of your hand. On the front, the D4 SSD is completely bare aside from a small sticker with D4 SSD printed on it; both sides are the same, with the TERRAMASTER logo stamped in the center. Unlike the D5-, D8 Hybrid, and NAS' in the same class (2- and 4-bay,) the logos do not double as ventilation on the D4 SSD. Around the back is a pretty bare affair with regulatory information stamped on it, then you have the Type C USB4 port and barrel power port input along with the screw that once removed, lets you slide off the cover to access the internals and manage the M.2 SSDs. Top Bottom The top uses the full surface area aside from the power button to assist with ventilation, and on the bottom, there are two 50 x 50 x 10mm intake fans that are very quiet. Installation Well, like the D9-320, there's hardly anything to it. Take off the screw around the back and screw in your PCIe NVMe M.2 2280 SSDs. They run at a (combined) max speed of USB4 (40 Gbps). TerraMaster includes a screw on each M2 connector, so need to go hunting, there are also two "backup screws" included in the box. For our review, we used two MP44Q 4TB NVMe SSDs ($224.99 on Amazon or Newegg) that TEAMGROUP supplied us with, and a 2TB Rocket 4 Plus ($219.99 on Newegg) that Sabrent sent to us. They are all PCIe 4.0 x4 drives. TerraMaster also uploaded a video to YouTube that shows how to install the storage options. Usage First, a bit of background on the capabilities of the D4 SSD. The ASMedia ASM2464PDX chip offers four lanes at PCIe 4.0 x 1; however, you can only expect to see up to 3257 MB/s speeds, and that will need to be in a RAID configuration; it basically translates to speeds you would expect from a traditional PCIe 3.0 SSD. This drops to around half that speed if the disks are being used independently in SINGLE disk mode. Here is how TerraMaster breaks it down: Unlike the D9-320 that we recently tested, it is not possible to daisy chain the D4 SSD with multiple units. As of writing, TerraMaster is not offering it in any other sizes (so, there is no D8 SSD option). RAID Happily, you can create a Striped or Spanned Volume of the disks in Windows, but be aware that it will only combine the total size of the smallest-sized SSD (so if you have 2TB + 4TB + 4TB, a volume of 3x 2TB will be created). In TOS 6 the same is true with the default TRAID setting, which is basically TerraMaster's own flavor of RAID5. Creating a storage pool on the D4 SSD in TOS 6 Creating a 3.71TB Storage pool (using two 4TB SSDs in TRAID) took around three hours to synchronize. On the official website, it is suggested that you download TPC Backupper, which is not included in the box, on a USB or onboard storage in the D8 Hybrid. There's a card that also instructs to download TPC Backupper. Still, I find that a bit of a shame because even most Razer or Logitech keyboards and mice include the setup program for Synapse or Logitech Options when you connect these devices to your Windows PC. Upon installing TPC Backupper by AOMEI a web page automatically opens in the default browser, thanking for a successful installation of what is actually a rebranded version of the free AOMEI Backupper Standard, and it "helpfully" suggests upgrading to a paid version for more features. The nag to upgrade to a paid version of the software seems a bit desperate if you ask me. I decided to emulate a daily backup that I usually do with the excellent SyncFolder, which basically backs up my Documents and Pictures folders from my main PC to my NAS Cloud drive. For this, I used the TPC Backupper app that I mentioned earlier. D4 SSD attached to local PC, local disk backup to D4 SSD over USB The process took a little under ten minutes to back up 34,979 files in 2,213 folders totaling 35,7GB into an .afi image file on a Striped volume. Restoring to the same local SSD only took 2m30s, which is impressive. D9-320 attached to local PC, backup to NAS over network Next, I backed up the same Documents and Pictures folders from the Striped volume in the D4 SSD to my Cloud backup over the network, and this took 11m20s. Restoring to the D4 SSD took just under three minutes, which is only half a minute longer than restoring the same data locally. Local PC backup over LAN to D4 SSD attached to NAS over USB Lastly, I ran the backup with the D4 SSD attached directly to my TerraMaster F4-424 Max over USB, so this meant copying the Documents and Pictures folder from my local PC over my LAN to the D4 SSD. The process took 14m33s to back up 34,979 files in 2,213 folders totaling 35,7GB into an .afi image file on the Simple volume, which is a little longer over the network than with the D4 SSD attached via USB to my local PC. Restoring the data locally over the network only took 1m30s, which was a minute quicker than restoring from the D4 SSD when attached locally, for some reason. Drive speed Striped volume Simple volume However, back to the drive setup, I ran CrystalDiskMark 8.0.5 in Windows 11 24H2 with the D4 SSD attached to that PC. I included both RAID and SINGLE disk mode, and the results definitely align with TerraMaster's drive speed claims, mentioned earlier in this review. I tried to measure the noise, but it did not register over the (roughly) 50dB of ambient noise of my work-from-home office. We will have to take TerraMaster's word for the claim about noise levels being as low as 19 dB. The Cooler Master NR200P Max towers above the TerraMaster D4 SSD Conclusion TerraMaster markets the D4 SSD as "specifically designed for media creation and video production applications," but also says that it "serves as an ideal external storage expansion solution for Mac mini and can be used as a Mac OS boot drive." Sorry, but I do not have a Mac mini to test this claim. TerraMaster also claims that this would suit gamers, for its "seamless experience indistinguishable from running on a local drive, with truly zero-latency performance." So it really has several use case applications depending on your wishes, and affordability to populate with up to four (large) SSDs. It looks premium, but it is what it is, essentially a plastic shell of a DAS. But it does not feel cheap either, the bottom intake fans are quiet, and overall, it is a nice-looking device that will not take up much room anywhere you place it. The added bonus here is RAID support, unlike with the D9-320 in Windows. However, do not expect RAID support on any NAS other than TerraMaster's own TOS 6 because you cannot create a storage pool over USB (at least in Synology DSM). Say you had a few one- or two-terabyte SSDs lying around, you could stick them all in and create a striped volume for anything up to 8TB for a really large storage volume in Windows. If I had any complaints at all, it would be how it does not really fully support 3rd party NAS' for creating a storage pool, but that would probably require an eSATA port. Secondly, I would have preferred to have seen a toolless method for installing and managing the SSDs. Most modern motherboards now use the toolless method of a clip or latch for M.2 SSDs, and given that the D4 SSD only supports 2280-sized SSDs, I don't feel this is a huge ask. You can purchase the TerraMaster D4 SSD for $299.99 from today (June 17) on the official website. As an Amazon Associate, we earn from qualifying purchases.
    • they are breaking stuff on purpose in the classic outlook to say look go over there! it's odd how since new outlook appeared old outlook as broke a LOT more then it used to
  • Recent Achievements

    • Experienced
      dismuter went up a rank
      Experienced
    • One Month Later
      mevinyavin earned a badge
      One Month Later
    • Week One Done
      rozermack875 earned a badge
      Week One Done
    • Week One Done
      oneworldtechnologies earned a badge
      Week One Done
    • Veteran
      matthiew went up a rank
      Veteran
  • Popular Contributors

    1. 1
      +primortal
      685
    2. 2
      ATLien_0
      266
    3. 3
      Michael Scrip
      206
    4. 4
      +FloatingFatMan
      185
    5. 5
      Steven P.
      142
  • Tell a friend

    Love Neowin? Tell a friend!