Hi,
Can someone explain the differences(set up, pre-main()
setup/initialization) between global variables in a C++ and a C program?
The global variables I used are uninitialized.
I have a test.o which declares a global int " int xxx;". Now I link
test.o to a FreeBSD kernel module which then tries to access xxx. If
test.o was compiled from C source the kernel can access the global
variable (which should be of course its own copy in kernel space and not
the test.o linked to the user-space application process). But if the
test.o was generated from C++ source and libstdc++ etc. are linked to
the kernel module then the kernel freezes upon accessing xxx.
Before accessing the integer xxx, I do set the CR3 memory address-space
context for the user process address space. So that the address space
for the user process becomes visible to the kernel(as often happens with
a system call).
My only question is : why can the kernel access the global variable xxx
in a C program but fails in case of a global int in a C++ program? Is it
because of the constructor support for the C++ object file or things
called before C++ main() etc.? Or is there any other reason?
Any help is appreciated.
Thanx,
Anand 2 2181
"Anand Subramanian" <an***@cs.uwate rloo.ca> wrote in message
news:cb******** **@rumours.uwat erloo.ca... Hi, Can someone explain the differences(set up, pre-main() setup/initialization) between global variables in a C++ and a C program? The global variables I used are uninitialized.
I have a test.o which declares a global int " int xxx;". Now I link test.o to a FreeBSD kernel module which then tries to access xxx. If test.o was compiled from C source the kernel can access the global variable (which should be of course its own copy in kernel space and not the test.o linked to the user-space application process). But if the test.o was generated from C++ source and libstdc++ etc. are linked to the kernel module then the kernel freezes upon accessing xxx.
Before accessing the integer xxx, I do set the CR3 memory address-space context for the user process address space. So that the address space for the user process becomes visible to the kernel(as often happens with a system call).
My only question is : why can the kernel access the global variable xxx in a C program but fails in case of a global int in a C++ program? Is it because of the constructor support for the C++ object file or things called before C++ main() etc.? Or is there any other reason?
Any help is appreciated.
I think you want news:comp.unix. programmer . There is too much platform
specific stuff in your question for you to be on topic in this group.
john
Anand Subramanian posted: Hi, Can someone explain the differences(set up, pre-main() setup/initialization) between global variables in a C++ and a C program? The global variables I used are uninitialized.
I have a test.o which declares a global int " int xxx;". Now I link test.o to a FreeBSD kernel module which then tries to access xxx. If test.o was compiled from C source the kernel can access the global variable (which should be of course its own copy in kernel space and not the test.o linked to the user-space application process). But if the test.o was generated from C++ source and libstdc++ etc. are linked to the kernel module then the kernel freezes upon accessing xxx.
Before accessing the integer xxx, I do set the CR3 memory address-space context for the user process address space. So that the address space for the user process becomes visible to the kernel(as often happens with a system call).
My only question is : why can the kernel access the global variable xxx in a C program but fails in case of a global int in a C++ program? Is it because of the constructor support for the C++ object file or things called before C++ main() etc.? Or is there any other reason?
Any help is appreciated.
Thanx, Anand
Just a thought, but it might be the following problem:
ClassA ObjectA;
ClassB ObjectB = ObjectA.MakeB() ;
Global objects/variables are allocated/constructed in no particular order in
a C++ program. If this is your problem, there's a solution in the FAQ.
-JKop This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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