关于Symbian的"crosses initialization of XXX"错误

最新推荐文章于 2024-01-15 09:41:18 发布

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最新推荐文章于 2024-01-15 09:41:18 发布

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分类专栏： Symbian 文章标签： initialization symbian compiler object constructor google

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本文介绍了一种在编译过程中出现的crossesinitialization错误及其解决方案。此错误源于switch语句中变量作用域的问题，通过使用大括号限定变量作用域可以避免此错误。

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昨天，同事在把前一阶段的项目编译、打包成sis安装文件时，遇到如下的编译错误：

crosses initialization of XXX

同事向我请教，我仔细看了一下他的代码，并没有什么问题。这个错误提示很少见，于是Google了一下，找到如下一篇论坛上的资料：

Problem: You get an error of this form, while compiling some nice program from source:

Code:

error: jump to case label
error: crosses initialization of `bool pushed'

The offending code contains a switch statement and a declaration of some variable or object inside one of its cases:

Code:

case HD_ELEMENT_UL :
bool pushed = t->style->margin[HD_POS_LEFT] != 0.0 ||
t->style->margin[HD_POS_RIGHT] != 0.0;

if (pushed)
margins->push(margins->left() + t->style->margin[HD_POS_LEFT],
margins->right() - t->style->margin[HD_POS_RIGHT],
margins->bottom(), 0);

parse_contents(t->child, margins, y, page, heading, chap);

if (pushed)
margins->pop();
break;

Reason: The problem is that there is a declaration of an object (the boolean "pushed") without scope. Thus, the scope of the object could traverse the break statement and apply to the next case. Consider this - what is the scope of obj1 in the code below? It starts at the first label, and goes until the end of the case block. So it's in scope at CHOICE_B. But its constructor wasn't called....

Code:

switch (choice) {
case CHOICE_A:
someclass obj1(&commonobj);

break;
case CHOICE_B:
someotherclass obj2(&commonobj);

break;
default:
break;
}
}

Thus, you should use curly brackets to delimit scope, as in:

Code:

switch (choice) {
case A: {
someobj x;
...
}
break;
case B: {
...
}
break;
...
}

Solution: Change the case statement to:

Code:

case HD_ELEMENT_UL :
{
bool pushed = t->style->margin[HD_POS_LEFT] != 0.0 ||
t->style->margin[HD_POS_RIGHT] != 0.0;

if (pushed)
margins->push(margins->left() + t->style->margin[HD_POS_LEFT],
margins->right() - t->style->margin[HD_POS_RIGHT],
margins->bottom(), 0);

parse_contents(t->child, margins, y, page, heading, chap);

if (pushed)
margins->pop();
}
break;

i.e. add curly brackets to delimit the scope of "pushed" inside the switch.

Exclamation References:

Bug#180937: g++ internal compiler error: Error reporting routines re-entered

Bug#180937: g++ internal compiler error: Error reporting routines re-entered
_________________
Regards

Chris Karakas
www.karakas-online.de