Connect two third party modules with “const char*” and “char*” arguments
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I have two third party modules and I have to combine them.
First I get data from a class. I will submit this data to a function.
bool loadLibrary(const char *strPlugName){
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
return false;
}
The const char * strPlugName is a value that I got from another library. I cannot change this value type myself.
Inside the function I try to call a BASS Library function.
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
Definition: typedef HPLUGIN (*BASS_PluginLoad_Type)(char *file,DWORD flags);
Here Xcode tell me:
Cannot initialize a parameter of type 'char *' with an rvalue of type 'const char *'
My question is how I can convert or cast this const char * to char *?
c++
edited Apr 2 at 7:30
StoryTeller
106k13222285
asked Apr 2 at 7:12
Thomas DThomas D
585
add a comment |
I have two third party modules and I have to combine them.
First I get data from a class. I will submit this data to a function.
bool loadLibrary(const char *strPlugName){
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
return false;
}
The const char * strPlugName is a value that I got from another library. I cannot change this value type myself.
Inside the function I try to call a BASS Library function.
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
Definition: typedef HPLUGIN (*BASS_PluginLoad_Type)(char *file,DWORD flags);
Here Xcode tell me:
Cannot initialize a parameter of type 'char *' with an rvalue of type 'const char *'
My question is how I can convert or cast this const char * to char *?
c++
edited Apr 2 at 7:30
StoryTeller
106k13222285
asked Apr 2 at 7:12
Thomas DThomas D
585
Not to get crucified, but const_cast ... ouch...
– user1810087
Apr 2 at 7:16
add a comment |
I have two third party modules and I have to combine them.
First I get data from a class. I will submit this data to a function.
bool loadLibrary(const char *strPlugName){
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
return false;
}
The const char * strPlugName is a value that I got from another library. I cannot change this value type myself.
Inside the function I try to call a BASS Library function.
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
Definition: typedef HPLUGIN (*BASS_PluginLoad_Type)(char *file,DWORD flags);
Here Xcode tell me:
Cannot initialize a parameter of type 'char *' with an rvalue of type 'const char *'
My question is how I can convert or cast this const char * to char *?
c++
edited Apr 2 at 7:30
StoryTeller
106k13222285
asked Apr 2 at 7:12
Thomas DThomas D
585
I have two third party modules and I have to combine them.
First I get data from a class. I will submit this data to a function.
bool loadLibrary(const char *strPlugName){
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
return false;
}
The const char * strPlugName is a value that I got from another library. I cannot change this value type myself.
Inside the function I try to call a BASS Library function.
HPLUGIN temp = _BASS_PluginLoad(strPlugName,0);
Definition: typedef HPLUGIN (*BASS_PluginLoad_Type)(char *file,DWORD flags);
Here Xcode tell me:
Cannot initialize a parameter of type 'char *' with an rvalue of type 'const char *'
My question is how I can convert or cast this const char * to char *?
c++
c++
edited Apr 2 at 7:30
StoryTeller
106k13222285
asked Apr 2 at 7:12
Thomas DThomas D
585
edited Apr 2 at 7:30
StoryTeller
106k13222285
asked Apr 2 at 7:12
Thomas DThomas D
585
edited Apr 2 at 7:30
StoryTeller
106k13222285
edited Apr 2 at 7:30
StoryTeller
106k13222285
edited Apr 2 at 7:30
StoryTeller
106k13222285
106k13222285
asked Apr 2 at 7:12
Thomas DThomas D
585
asked Apr 2 at 7:12
Thomas DThomas D
585
asked Apr 2 at 7:12
Thomas DThomas D
585
585
Not to get crucified, but const_cast ... ouch...
– user1810087
Apr 2 at 7:16
add a comment |
Not to get crucified, but const_cast ... ouch...
– user1810087
Apr 2 at 7:16
Not to get crucified, but const_cast ... ouch...
– user1810087
Apr 2 at 7:16
Not to get crucified, but const_cast ... ouch...
– user1810087
Apr 2 at 7:16
add a comment |
2 Answers
2
active
oldest
votes
If and only if the function called via _BASS_PluginLoad doesn't alter the memory pointed at by file, you can use a const_cast:
HPLUGIN temp = _BASS_PluginLoad(const_cast<char*>(strPlugName),0);
Some old c API's are not const correct on account of the const keyword being a fairly late addition to the C language. But they still don't mutate their arguments, so a const_cast is the easiest way to make use of them in const correct C++ wrappers. It's a perfectly legitimate reason (maybe even the reason) for that cast.
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
1
Note that only some APIs can be fixed like this. Others actually do temporarily mutate their argument. (There's a notorious Win32 API which does this, but I can't remember which it is.)
– Martin Bonner
Apr 2 at 7:28
add a comment |
The easy and safe way is to copy the argument into a local buffer, and then pass a pointer to that. As you are using C++, you can automate the memory management.
bool loadLibrary(const char *strPlugName){
std::string local(strPlugName);
local.push_back(''); // Ensure null terminated, if not using C++11 or greater
HPLUGIN temp = _BASS_PluginLoad(&local[0],0);
return false;
}
If using C++17, you can just call local.data() instead of &local[0].
Language lawyer caveat:
Strictly speaking, &local[0] was not defined to work in C++98 - in practice it always did (and later versions of the standard defined it to work).
edited Apr 2 at 13:54
Toby Speight
17.6k134469
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
You can skip the null termination since C++11 if memory serves. You do need C++17 for the const correctlocal.data()however.
– StoryTeller
Apr 2 at 7:29
@StoryTellerlocal.data()is null-terminated in C++11, but I'm not sure&local[0]is - BICBW.
– Martin Bonner
Apr 2 at 7:32
They both produce the same buffer (as doesc_str) since C++11. The null terminator is guaranteed.
– StoryTeller
Apr 2 at 7:33
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
If and only if the function called via _BASS_PluginLoad doesn't alter the memory pointed at by file, you can use a const_cast:
HPLUGIN temp = _BASS_PluginLoad(const_cast<char*>(strPlugName),0);
Some old c API's are not const correct on account of the const keyword being a fairly late addition to the C language. But they still don't mutate their arguments, so a const_cast is the easiest way to make use of them in const correct C++ wrappers. It's a perfectly legitimate reason (maybe even the reason) for that cast.
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
1
Note that only some APIs can be fixed like this. Others actually do temporarily mutate their argument. (There's a notorious Win32 API which does this, but I can't remember which it is.)
– Martin Bonner
Apr 2 at 7:28
add a comment |
If and only if the function called via _BASS_PluginLoad doesn't alter the memory pointed at by file, you can use a const_cast:
HPLUGIN temp = _BASS_PluginLoad(const_cast<char*>(strPlugName),0);
Some old c API's are not const correct on account of the const keyword being a fairly late addition to the C language. But they still don't mutate their arguments, so a const_cast is the easiest way to make use of them in const correct C++ wrappers. It's a perfectly legitimate reason (maybe even the reason) for that cast.
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
1
Note that only some APIs can be fixed like this. Others actually do temporarily mutate their argument. (There's a notorious Win32 API which does this, but I can't remember which it is.)
– Martin Bonner
Apr 2 at 7:28
add a comment |
If and only if the function called via _BASS_PluginLoad doesn't alter the memory pointed at by file, you can use a const_cast:
HPLUGIN temp = _BASS_PluginLoad(const_cast<char*>(strPlugName),0);
Some old c API's are not const correct on account of the const keyword being a fairly late addition to the C language. But they still don't mutate their arguments, so a const_cast is the easiest way to make use of them in const correct C++ wrappers. It's a perfectly legitimate reason (maybe even the reason) for that cast.
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
If and only if the function called via _BASS_PluginLoad doesn't alter the memory pointed at by file, you can use a const_cast:
HPLUGIN temp = _BASS_PluginLoad(const_cast<char*>(strPlugName),0);
Some old c API's are not const correct on account of the const keyword being a fairly late addition to the C language. But they still don't mutate their arguments, so a const_cast is the easiest way to make use of them in const correct C++ wrappers. It's a perfectly legitimate reason (maybe even the reason) for that cast.
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
edited Apr 2 at 7:36
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
answered Apr 2 at 7:16
StoryTellerStoryTeller
106k13222285
106k13222285
1
Note that only some APIs can be fixed like this. Others actually do temporarily mutate their argument. (There's a notorious Win32 API which does this, but I can't remember which it is.)
– Martin Bonner
Apr 2 at 7:28
add a comment |
1
Note that only some APIs can be fixed like this. Others actually do temporarily mutate their argument. (There's a notorious Win32 API which does this, but I can't remember which it is.)
– Martin Bonner
Apr 2 at 7:28
1
1
Note that only some APIs can be fixed like this. Others actually do temporarily mutate their argument. (There's a notorious Win32 API which does this, but I can't remember which it is.)
– Martin Bonner
Apr 2 at 7:28
Note that only some APIs can be fixed like this. Others actually do temporarily mutate their argument. (There's a notorious Win32 API which does this, but I can't remember which it is.)
– Martin Bonner
Apr 2 at 7:28
add a comment |
The easy and safe way is to copy the argument into a local buffer, and then pass a pointer to that. As you are using C++, you can automate the memory management.
bool loadLibrary(const char *strPlugName){
std::string local(strPlugName);
local.push_back(''); // Ensure null terminated, if not using C++11 or greater
HPLUGIN temp = _BASS_PluginLoad(&local[0],0);
return false;
}
If using C++17, you can just call local.data() instead of &local[0].
Language lawyer caveat:
Strictly speaking, &local[0] was not defined to work in C++98 - in practice it always did (and later versions of the standard defined it to work).
edited Apr 2 at 13:54
Toby Speight
17.6k134469
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
You can skip the null termination since C++11 if memory serves. You do need C++17 for the const correctlocal.data()however.
– StoryTeller
Apr 2 at 7:29
@StoryTellerlocal.data()is null-terminated in C++11, but I'm not sure&local[0]is - BICBW.
– Martin Bonner
Apr 2 at 7:32
They both produce the same buffer (as doesc_str) since C++11. The null terminator is guaranteed.
– StoryTeller
Apr 2 at 7:33
add a comment |
The easy and safe way is to copy the argument into a local buffer, and then pass a pointer to that. As you are using C++, you can automate the memory management.
bool loadLibrary(const char *strPlugName){
std::string local(strPlugName);
local.push_back(''); // Ensure null terminated, if not using C++11 or greater
HPLUGIN temp = _BASS_PluginLoad(&local[0],0);
return false;
}
If using C++17, you can just call local.data() instead of &local[0].
Language lawyer caveat:
Strictly speaking, &local[0] was not defined to work in C++98 - in practice it always did (and later versions of the standard defined it to work).
edited Apr 2 at 13:54
Toby Speight
17.6k134469
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
You can skip the null termination since C++11 if memory serves. You do need C++17 for the const correctlocal.data()however.
– StoryTeller
Apr 2 at 7:29
@StoryTellerlocal.data()is null-terminated in C++11, but I'm not sure&local[0]is - BICBW.
– Martin Bonner
Apr 2 at 7:32
They both produce the same buffer (as doesc_str) since C++11. The null terminator is guaranteed.
– StoryTeller
Apr 2 at 7:33
add a comment |
The easy and safe way is to copy the argument into a local buffer, and then pass a pointer to that. As you are using C++, you can automate the memory management.
bool loadLibrary(const char *strPlugName){
std::string local(strPlugName);
local.push_back(''); // Ensure null terminated, if not using C++11 or greater
HPLUGIN temp = _BASS_PluginLoad(&local[0],0);
return false;
}
If using C++17, you can just call local.data() instead of &local[0].
Language lawyer caveat:
Strictly speaking, &local[0] was not defined to work in C++98 - in practice it always did (and later versions of the standard defined it to work).
edited Apr 2 at 13:54
Toby Speight
17.6k134469
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
The easy and safe way is to copy the argument into a local buffer, and then pass a pointer to that. As you are using C++, you can automate the memory management.
bool loadLibrary(const char *strPlugName){
std::string local(strPlugName);
local.push_back(''); // Ensure null terminated, if not using C++11 or greater
HPLUGIN temp = _BASS_PluginLoad(&local[0],0);
return false;
}
If using C++17, you can just call local.data() instead of &local[0].
Language lawyer caveat:
Strictly speaking, &local[0] was not defined to work in C++98 - in practice it always did (and later versions of the standard defined it to work).
edited Apr 2 at 13:54
Toby Speight
17.6k134469
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
edited Apr 2 at 13:54
Toby Speight
17.6k134469
edited Apr 2 at 13:54
Toby Speight
17.6k134469
edited Apr 2 at 13:54
Toby Speight
17.6k134469
17.6k134469
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
answered Apr 2 at 7:26
Martin BonnerMartin Bonner
23.8k33267
23.8k33267
You can skip the null termination since C++11 if memory serves. You do need C++17 for the const correctlocal.data()however.
– StoryTeller
Apr 2 at 7:29
@StoryTellerlocal.data()is null-terminated in C++11, but I'm not sure&local[0]is - BICBW.
– Martin Bonner
Apr 2 at 7:32
They both produce the same buffer (as doesc_str) since C++11. The null terminator is guaranteed.
– StoryTeller
Apr 2 at 7:33
add a comment |
You can skip the null termination since C++11 if memory serves. You do need C++17 for the const correctlocal.data()however.
– StoryTeller
Apr 2 at 7:29
@StoryTellerlocal.data()is null-terminated in C++11, but I'm not sure&local[0]is - BICBW.
– Martin Bonner
Apr 2 at 7:32
They both produce the same buffer (as doesc_str) since C++11. The null terminator is guaranteed.
– StoryTeller
Apr 2 at 7:33
You can skip the null termination since C++11 if memory serves. You do need C++17 for the const correct
local.data() however.– StoryTeller
Apr 2 at 7:29
You can skip the null termination since C++11 if memory serves. You do need C++17 for the const correct
local.data() however.– StoryTeller
Apr 2 at 7:29
@StoryTeller
local.data() is null-terminated in C++11, but I'm not sure &local[0] is - BICBW.– Martin Bonner
Apr 2 at 7:32
@StoryTeller
local.data() is null-terminated in C++11, but I'm not sure &local[0] is - BICBW.– Martin Bonner
Apr 2 at 7:32
They both produce the same buffer (as does
c_str) since C++11. The null terminator is guaranteed.– StoryTeller
Apr 2 at 7:33
They both produce the same buffer (as does
c_str) since C++11. The null terminator is guaranteed.– StoryTeller
Apr 2 at 7:33
add a comment |
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Not to get crucified, but const_cast ... ouch...
– user1810087
Apr 2 at 7:16