Nested std::bind in lambda cannot be casted to std::function (from void*)
0
I have to cast a member method call (SystemUpdater::OnSystemUpdateCompletedHandler) to void* in order to access as argument in a static C function.
Snippet 1:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, std::bind(&SystemUpdater::OnSystemUpdateCompletedHandler, this, std::placeholders::_1));
Snippet 2:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, [&](int result)OnSystemUpdateCompletedHandler(result); );
The second argument of StartUpdate is casted and executed in my static C function:
(*((std::function<void(int)>*) userdata))(_result);
This cast and execution works with snippet 2 but NOT with snippet 1 (Signal: SIGSEGV (Segmentation fault)).
Why?
StartUpdate is declared as:
UpdateResult_t StartUpdate(const std::string &path,const std::function<void(int)> &finishCallback)
c++ lambda std-function stdbind
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
|
show 1 more comment
0
I have to cast a member method call (SystemUpdater::OnSystemUpdateCompletedHandler) to void* in order to access as argument in a static C function.
Snippet 1:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, std::bind(&SystemUpdater::OnSystemUpdateCompletedHandler, this, std::placeholders::_1));
Snippet 2:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, [&](int result)OnSystemUpdateCompletedHandler(result); );
The second argument of StartUpdate is casted and executed in my static C function:
(*((std::function<void(int)>*) userdata))(_result);
This cast and execution works with snippet 2 but NOT with snippet 1 (Signal: SIGSEGV (Segmentation fault)).
Why?
StartUpdate is declared as:
UpdateResult_t StartUpdate(const std::string &path,const std::function<void(int)> &finishCallback)
c++ lambda std-function stdbind
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
2
You know, that a lambda is not a pointer to anstd::functionand that your second snippet is probably only working because theoperator ()ofstd::functionin the compiler you are using just happens to also work whenthisis pointing to certain lambda types? Or is your code ofStartUpdatedoing something to get thatuserdatato anstd::functionpointer?
– Yanick Salzmann
Nov 15 '18 at 13:32
1
Please be more specific than ”it doesn’t work”. And read about the Minimal, Complete, and Verifiable example.
– molbdnilo
Nov 15 '18 at 13:35
@JeJo theresultis whats passed through thestd::placeholders::_1to the bound function.
– Yanick Salzmann
Nov 15 '18 at 13:37
Thanks for your replys! @molbdnilo I know that my question is not that clear - thank you for the information. I will try to be more specific.
– Fabian Knapp
Nov 15 '18 at 13:46
@yanick-salzmann I have added the declaration of StartUpdate. I dont do any magic with userdata in StartUpdate.
– Fabian Knapp
Nov 15 '18 at 13:46
|
show 1 more comment
0
0
0
I have to cast a member method call (SystemUpdater::OnSystemUpdateCompletedHandler) to void* in order to access as argument in a static C function.
Snippet 1:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, std::bind(&SystemUpdater::OnSystemUpdateCompletedHandler, this, std::placeholders::_1));
Snippet 2:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, [&](int result)OnSystemUpdateCompletedHandler(result); );
The second argument of StartUpdate is casted and executed in my static C function:
(*((std::function<void(int)>*) userdata))(_result);
This cast and execution works with snippet 2 but NOT with snippet 1 (Signal: SIGSEGV (Segmentation fault)).
Why?
StartUpdate is declared as:
UpdateResult_t StartUpdate(const std::string &path,const std::function<void(int)> &finishCallback)
c++ lambda std-function stdbind
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
I have to cast a member method call (SystemUpdater::OnSystemUpdateCompletedHandler) to void* in order to access as argument in a static C function.
Snippet 1:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, std::bind(&SystemUpdater::OnSystemUpdateCompletedHandler, this, std::placeholders::_1));
Snippet 2:
updateDownloader->StartDownloadAsync(_updateRequest.url, "update-test", [&](std::string resultFile, Network::FileDownloaderResult_t result) {
this->updateHelper->StartUpdate(resultFile, [&](int result)OnSystemUpdateCompletedHandler(result); );
The second argument of StartUpdate is casted and executed in my static C function:
(*((std::function<void(int)>*) userdata))(_result);
This cast and execution works with snippet 2 but NOT with snippet 1 (Signal: SIGSEGV (Segmentation fault)).
Why?
StartUpdate is declared as:
UpdateResult_t StartUpdate(const std::string &path,const std::function<void(int)> &finishCallback)
c++ lambda std-function stdbind
c++ lambda std-function stdbind
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
edited Nov 15 '18 at 13:42
Fabian Knapp
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
asked Nov 15 '18 at 13:21
Fabian KnappFabian Knapp
1,1661020
1,1661020
2
You know, that a lambda is not a pointer to anstd::functionand that your second snippet is probably only working because theoperator ()ofstd::functionin the compiler you are using just happens to also work whenthisis pointing to certain lambda types? Or is your code ofStartUpdatedoing something to get thatuserdatato anstd::functionpointer?
– Yanick Salzmann
Nov 15 '18 at 13:32
1
Please be more specific than ”it doesn’t work”. And read about the Minimal, Complete, and Verifiable example.
– molbdnilo
Nov 15 '18 at 13:35
@JeJo theresultis whats passed through thestd::placeholders::_1to the bound function.
– Yanick Salzmann
Nov 15 '18 at 13:37
Thanks for your replys! @molbdnilo I know that my question is not that clear - thank you for the information. I will try to be more specific.
– Fabian Knapp
Nov 15 '18 at 13:46
@yanick-salzmann I have added the declaration of StartUpdate. I dont do any magic with userdata in StartUpdate.
– Fabian Knapp
Nov 15 '18 at 13:46
|
show 1 more comment
2
You know, that a lambda is not a pointer to anstd::functionand that your second snippet is probably only working because theoperator ()ofstd::functionin the compiler you are using just happens to also work whenthisis pointing to certain lambda types? Or is your code ofStartUpdatedoing something to get thatuserdatato anstd::functionpointer?
– Yanick Salzmann
Nov 15 '18 at 13:32
1
Please be more specific than ”it doesn’t work”. And read about the Minimal, Complete, and Verifiable example.
– molbdnilo
Nov 15 '18 at 13:35
@JeJo theresultis whats passed through thestd::placeholders::_1to the bound function.
– Yanick Salzmann
Nov 15 '18 at 13:37
Thanks for your replys! @molbdnilo I know that my question is not that clear - thank you for the information. I will try to be more specific.
– Fabian Knapp
Nov 15 '18 at 13:46
@yanick-salzmann I have added the declaration of StartUpdate. I dont do any magic with userdata in StartUpdate.
– Fabian Knapp
Nov 15 '18 at 13:46
2
2
You know, that a lambda is not a pointer to an
std::function and that your second snippet is probably only working because the operator () of std::function in the compiler you are using just happens to also work when this is pointing to certain lambda types? Or is your code of StartUpdate doing something to get that userdata to an std::function pointer?– Yanick Salzmann
Nov 15 '18 at 13:32
You know, that a lambda is not a pointer to an
std::function and that your second snippet is probably only working because the operator () of std::function in the compiler you are using just happens to also work when this is pointing to certain lambda types? Or is your code of StartUpdate doing something to get that userdata to an std::function pointer?– Yanick Salzmann
Nov 15 '18 at 13:32
1
1
Please be more specific than ”it doesn’t work”. And read about the Minimal, Complete, and Verifiable example.
– molbdnilo
Nov 15 '18 at 13:35
Please be more specific than ”it doesn’t work”. And read about the Minimal, Complete, and Verifiable example.
– molbdnilo
Nov 15 '18 at 13:35
@JeJo the
result is whats passed through the std::placeholders::_1 to the bound function.– Yanick Salzmann
Nov 15 '18 at 13:37
@JeJo the
result is whats passed through the std::placeholders::_1 to the bound function.– Yanick Salzmann
Nov 15 '18 at 13:37
Thanks for your replys! @molbdnilo I know that my question is not that clear - thank you for the information. I will try to be more specific.
– Fabian Knapp
Nov 15 '18 at 13:46
Thanks for your replys! @molbdnilo I know that my question is not that clear - thank you for the information. I will try to be more specific.
– Fabian Knapp
Nov 15 '18 at 13:46
@yanick-salzmann I have added the declaration of StartUpdate. I dont do any magic with userdata in StartUpdate.
– Fabian Knapp
Nov 15 '18 at 13:46
@yanick-salzmann I have added the declaration of StartUpdate. I dont do any magic with userdata in StartUpdate.
– Fabian Knapp
Nov 15 '18 at 13:46
|
show 1 more comment
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2
You know, that a lambda is not a pointer to an
std::functionand that your second snippet is probably only working because theoperator ()ofstd::functionin the compiler you are using just happens to also work whenthisis pointing to certain lambda types? Or is your code ofStartUpdatedoing something to get thatuserdatato anstd::functionpointer?– Yanick Salzmann
Nov 15 '18 at 13:32
1
Please be more specific than ”it doesn’t work”. And read about the Minimal, Complete, and Verifiable example.
– molbdnilo
Nov 15 '18 at 13:35
@JeJo the
resultis whats passed through thestd::placeholders::_1to the bound function.– Yanick Salzmann
Nov 15 '18 at 13:37
Thanks for your replys! @molbdnilo I know that my question is not that clear - thank you for the information. I will try to be more specific.
– Fabian Knapp
Nov 15 '18 at 13:46
@yanick-salzmann I have added the declaration of StartUpdate. I dont do any magic with userdata in StartUpdate.
– Fabian Knapp
Nov 15 '18 at 13:46