20.3.1.1. Globals and const | ||
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 | 20.3.1. Globals, static, and QObject |  |
20.3.1.1. Globals and const | ||
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| | 20.3.1. Globals, static, and QObject | |
[ fromfile: globals.xml id: constglobals ]
The scope of const global variables is slightly different from the scope of regular globals.
A global object that has been declared const has file scope, by default.
Unlike static objects declared outside of all blocks, it is possible to export a global const to other files by declaring it extern at the point where it is initialized.
For example, in one file, you could have the code in Example 20.8.
Example 20.8. src/const/globals/chunk1.cpp
const int NN = 10; // file scope
const int MM = 44; // file scope
extern const int QQ = 7; // can be accessed from other files
int main() {
// NN = 12; // error
int array[NN]; // okay
// QQ++; // error
double darray[QQ];
return 0;
}
In another file, you might have the code in Example 20.9
Example 20.9. src/const/globals/chunk2.cpp
extern const int NN = 22; // a different constant
extern const int MM; // error
// declare global constant - storage allocated elsewhere
extern const int QQ; // external declaration
void newFunction() {
int x = QQ + NN;
}
| Generated: 2012-03-02 | © 2012 Alan Ezust and Paul Ezust. |
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20.3.1. Globals, static, and QObject |  | 20.3.2. Exercises: Storage Class |