How to enable _all_ warnings with -fpermissive from g++?
There seem to be cases where the -fpermissive option results in errors being ignored altogether, rather than "downgraded" to warnings, as widely available documentation suggests.
The -Wall option is clearly not enough. What other options are needed in order to have all such downgraded warnings reported by g++?
An example came up with the Nodejs C++ addon library.
In file included from /opt/nodejs/linux64/8.9.4/include/node/node.h:63:0,
from /opt/nan/linux64/2.9.2/include/nan.h:51,
from /build/ndjs/include/blob.h:59,
from /build/ndjs/src/blob.cpp:2:
/opt/nodejs/linux64/8.9.4/include/node/v8.h: In instantiation of ‘v8::Local<T>::Local(v8::Local<S>) [with S = v8::Integer; T = v8::Int32]’:
/build/src/ndjs/blob.cpp:507:1: required from here
/opt/nodejs/linux64/8.9.4/include/node/v8.h:207:5: error: invalid conversion from ‘v8::Integer*’ to ‘v8::Int32*’ [-fpermissive]
TYPE_CHECK(T, S);
^
Recompiling with -fpermissive (and -Wall, of course) results in a clean compile: no warnings at all. What happened? (i.e. Why?)
The TYPE_CHECK() macro tests for type compatibility in pointer assignments:
#define TYPE_CHECK(T, S)
while (false) {
*(static_cast<T* volatile*>(0)) = static_cast<S*>(0);
}
It fails for downcasts (v8::Int32 is derived from v8::Integer), but somehow succeeds without warnings when -fpermissive is in effect. Shouldn't there be a warning about the static downcast?
c++ g++
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
add a comment |
There seem to be cases where the -fpermissive option results in errors being ignored altogether, rather than "downgraded" to warnings, as widely available documentation suggests.
The -Wall option is clearly not enough. What other options are needed in order to have all such downgraded warnings reported by g++?
An example came up with the Nodejs C++ addon library.
In file included from /opt/nodejs/linux64/8.9.4/include/node/node.h:63:0,
from /opt/nan/linux64/2.9.2/include/nan.h:51,
from /build/ndjs/include/blob.h:59,
from /build/ndjs/src/blob.cpp:2:
/opt/nodejs/linux64/8.9.4/include/node/v8.h: In instantiation of ‘v8::Local<T>::Local(v8::Local<S>) [with S = v8::Integer; T = v8::Int32]’:
/build/src/ndjs/blob.cpp:507:1: required from here
/opt/nodejs/linux64/8.9.4/include/node/v8.h:207:5: error: invalid conversion from ‘v8::Integer*’ to ‘v8::Int32*’ [-fpermissive]
TYPE_CHECK(T, S);
^
Recompiling with -fpermissive (and -Wall, of course) results in a clean compile: no warnings at all. What happened? (i.e. Why?)
The TYPE_CHECK() macro tests for type compatibility in pointer assignments:
#define TYPE_CHECK(T, S)
while (false) {
*(static_cast<T* volatile*>(0)) = static_cast<S*>(0);
}
It fails for downcasts (v8::Int32 is derived from v8::Integer), but somehow succeeds without warnings when -fpermissive is in effect. Shouldn't there be a warning about the static downcast?
c++ g++
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
1
-fpermissiveis supposed to be used for compiler development / testing purposes, you should never use it to compile regular code and / or expect to get any particular results from doing so.
– VTT
Nov 19 '18 at 16:59
-fpermissivehappened. If you have to tell the compiler to devieate from the standard then you probably need to rethink what your doing in the first place. -Wall is your default.
– johnathan
Nov 19 '18 at 17:36
Instead of trashing -fpermissive, which I can do as well as anyone, please try to address the question: how are downgraded warnings enabled? This comes often when dealing with third party code.
– arayq2
Nov 19 '18 at 17:40
add a comment |
There seem to be cases where the -fpermissive option results in errors being ignored altogether, rather than "downgraded" to warnings, as widely available documentation suggests.
The -Wall option is clearly not enough. What other options are needed in order to have all such downgraded warnings reported by g++?
An example came up with the Nodejs C++ addon library.
In file included from /opt/nodejs/linux64/8.9.4/include/node/node.h:63:0,
from /opt/nan/linux64/2.9.2/include/nan.h:51,
from /build/ndjs/include/blob.h:59,
from /build/ndjs/src/blob.cpp:2:
/opt/nodejs/linux64/8.9.4/include/node/v8.h: In instantiation of ‘v8::Local<T>::Local(v8::Local<S>) [with S = v8::Integer; T = v8::Int32]’:
/build/src/ndjs/blob.cpp:507:1: required from here
/opt/nodejs/linux64/8.9.4/include/node/v8.h:207:5: error: invalid conversion from ‘v8::Integer*’ to ‘v8::Int32*’ [-fpermissive]
TYPE_CHECK(T, S);
^
Recompiling with -fpermissive (and -Wall, of course) results in a clean compile: no warnings at all. What happened? (i.e. Why?)
The TYPE_CHECK() macro tests for type compatibility in pointer assignments:
#define TYPE_CHECK(T, S)
while (false) {
*(static_cast<T* volatile*>(0)) = static_cast<S*>(0);
}
It fails for downcasts (v8::Int32 is derived from v8::Integer), but somehow succeeds without warnings when -fpermissive is in effect. Shouldn't there be a warning about the static downcast?
c++ g++
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
There seem to be cases where the -fpermissive option results in errors being ignored altogether, rather than "downgraded" to warnings, as widely available documentation suggests.
The -Wall option is clearly not enough. What other options are needed in order to have all such downgraded warnings reported by g++?
An example came up with the Nodejs C++ addon library.
In file included from /opt/nodejs/linux64/8.9.4/include/node/node.h:63:0,
from /opt/nan/linux64/2.9.2/include/nan.h:51,
from /build/ndjs/include/blob.h:59,
from /build/ndjs/src/blob.cpp:2:
/opt/nodejs/linux64/8.9.4/include/node/v8.h: In instantiation of ‘v8::Local<T>::Local(v8::Local<S>) [with S = v8::Integer; T = v8::Int32]’:
/build/src/ndjs/blob.cpp:507:1: required from here
/opt/nodejs/linux64/8.9.4/include/node/v8.h:207:5: error: invalid conversion from ‘v8::Integer*’ to ‘v8::Int32*’ [-fpermissive]
TYPE_CHECK(T, S);
^
Recompiling with -fpermissive (and -Wall, of course) results in a clean compile: no warnings at all. What happened? (i.e. Why?)
The TYPE_CHECK() macro tests for type compatibility in pointer assignments:
#define TYPE_CHECK(T, S)
while (false) {
*(static_cast<T* volatile*>(0)) = static_cast<S*>(0);
}
It fails for downcasts (v8::Int32 is derived from v8::Integer), but somehow succeeds without warnings when -fpermissive is in effect. Shouldn't there be a warning about the static downcast?
c++ g++
c++ g++
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
edited Nov 19 '18 at 18:03
arayq2
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
asked Nov 19 '18 at 16:52
arayq2arayq2
1,987916
1,987916
1
-fpermissiveis supposed to be used for compiler development / testing purposes, you should never use it to compile regular code and / or expect to get any particular results from doing so.
– VTT
Nov 19 '18 at 16:59
-fpermissivehappened. If you have to tell the compiler to devieate from the standard then you probably need to rethink what your doing in the first place. -Wall is your default.
– johnathan
Nov 19 '18 at 17:36
Instead of trashing -fpermissive, which I can do as well as anyone, please try to address the question: how are downgraded warnings enabled? This comes often when dealing with third party code.
– arayq2
Nov 19 '18 at 17:40
add a comment |
1
-fpermissiveis supposed to be used for compiler development / testing purposes, you should never use it to compile regular code and / or expect to get any particular results from doing so.
– VTT
Nov 19 '18 at 16:59
-fpermissivehappened. If you have to tell the compiler to devieate from the standard then you probably need to rethink what your doing in the first place. -Wall is your default.
– johnathan
Nov 19 '18 at 17:36
Instead of trashing -fpermissive, which I can do as well as anyone, please try to address the question: how are downgraded warnings enabled? This comes often when dealing with third party code.
– arayq2
Nov 19 '18 at 17:40
1
1
-fpermissive is supposed to be used for compiler development / testing purposes, you should never use it to compile regular code and / or expect to get any particular results from doing so.– VTT
Nov 19 '18 at 16:59
-fpermissive is supposed to be used for compiler development / testing purposes, you should never use it to compile regular code and / or expect to get any particular results from doing so.– VTT
Nov 19 '18 at 16:59
-fpermissive happened. If you have to tell the compiler to devieate from the standard then you probably need to rethink what your doing in the first place. -Wall is your default.– johnathan
Nov 19 '18 at 17:36
-fpermissive happened. If you have to tell the compiler to devieate from the standard then you probably need to rethink what your doing in the first place. -Wall is your default.– johnathan
Nov 19 '18 at 17:36
Instead of trashing -fpermissive, which I can do as well as anyone, please try to address the question: how are downgraded warnings enabled? This comes often when dealing with third party code.
– arayq2
Nov 19 '18 at 17:40
Instead of trashing -fpermissive, which I can do as well as anyone, please try to address the question: how are downgraded warnings enabled? This comes often when dealing with third party code.
– arayq2
Nov 19 '18 at 17:40
add a comment |
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1
-fpermissiveis supposed to be used for compiler development / testing purposes, you should never use it to compile regular code and / or expect to get any particular results from doing so.– VTT
Nov 19 '18 at 16:59
-fpermissivehappened. If you have to tell the compiler to devieate from the standard then you probably need to rethink what your doing in the first place. -Wall is your default.– johnathan
Nov 19 '18 at 17:36
Instead of trashing -fpermissive, which I can do as well as anyone, please try to address the question: how are downgraded warnings enabled? This comes often when dealing with third party code.
– arayq2
Nov 19 '18 at 17:40