objective-c - sizeof 在 iPad 1 上崩溃但不是 > iPad 1

Question

考虑这段代码：

CGFloat largerLineSpacing = kStreamCellParagraphSpacing;

CTParagraphStyleSetting paragraphSettings[1] = {
    { kCTParagraphStyleSpecifierParagraphSpacing, sizeof(CGFloat), &largerLineSpacing }
};
CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings, sizeof(*paragraphSettings));

此代码在 iPad 1 (5.1) 上运行时崩溃并出现 EXC_BAD_ACCESS，但在 5.1 模拟器或 iPad 3 (6.0) 上运行时不会。我的 C 很弱 - 我在 sizeof 上犯了一个愚蠢的错误吗？

Answer 1

CTParagraphStyleCreate的文档建议它的第二个参数给出数组中的CTParagraphStyleSetting实例数paragraphSettings（在您的情况下为 1），而不是数组的字节大小。

如果您将代码更改为

CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings, 1);

它应该工作。或者，如果您想应对将来添加更多设置，您可以尝试

int numElems = sizeof(paragraphSettings)/sizeof(paragraphSettings[0]);
CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings,
                                                            numElems);

Answer 2

静态 CFIndex 常量 settingCount = 1;

CTParagraphStyleSetting paragraphSettings[settingCount] = {
    { kCTParagraphStyleSpecifierParagraphSpacing, sizeof(CGFloat), &largerLineSpacing }
};

CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings, settingCount);