C 代码保留先前设置的字符

Question

我有一些在 Objective-C 应用程序中运行的 C 代码。我从互联网上获取了这段代码。

static void extract_app_name(const char *all_arguments, char **app_name) {
    char *full_path, *app_end, *app_begin; //, *app_name_temp;
    size_t diff;

    if (all_arguments == NULL || app_name == NULL) {
        return;
    }

    full_path = (char*)all_arguments + sizeof(int);

    app_end = strcasestr(full_path, ".app");
    if (app_end == NULL) {
        app_begin = strrchr(full_path, '/');
        if (app_begin != NULL) {                
            *app_name = malloc(app_begin+1);
            *app_name = strdup(app_begin+1);
        } else {                
            *app_name = strdup(full_path);
        }
    } else {            
        app_begin = app_end;
        while (*(--app_begin) != '/') {}
        diff = app_end - app_begin; 
        char *app_name_temp[diff]; // = malloc(diff);
        *app_name_temp = malloc(diff);
        *app_name = malloc(diff);
        strncpy(*app_name_temp, app_begin+1, diff-1);
        app_name_temp[diff]='\0';
        app_name = strcpy(*app_name, *app_name_temp);
    }
}

此代码的目的是从完整路径中提取应用程序名称。如果应用程序以 .app 扩展名命名，它将从 .app 的任何内容中提取名称。

例如以下内容:

extract_app_name("/Applications/Google Chrome.app/Contents/Versions/16.0.912.63/Google Chrome Helper.app/Contents/MacOS/Google Chrome Helper", &app_name);
NSLog(@"First App is: %s", app_name);

extract_app_name("/System/Library/Frameworks/QuickLook.framework/Resources/quicklookd.app/Contents/MacOS/quicklookd", &app_name);
NSLog(@"Next App is: %s", app_name);

extract_app_name("/System/Library/CoreServices/Dock.app/Contents/XPCServices/com.apple.dock.extra.xpc/Contents/MacOS/com.apple.dock.extra", &app_name);
NSLog(@"Next App is: %s", app_name);

extract_app_name("/Applications/Tiny", &app_name);
NSLog(@"Next App is: %s", app_name);

应该输出这个:

First App is: Google Chrome
Next App is: quicklookd
Next App is: Dock
Next app is: Tiny

一般来说，这是正确的。但如果我连续运行应用程序 4-5 次，我的输出有时并不总是有效。有时，应该输出 quicklookd 的第二个应用程序实际上会转储 quicklookdome(它保留第一个应用程序名称的一部分)。

我怀疑这与变量未正确初始化并保留内存中该位置已有的内容有关。我只是不太了解 C，无法准确指出它。

Answer 1

这就是，固定和简化的:

    static void extract_app_name(const char *all_arguments, char **app_name) {
        char *full_path, *app_end, *app_begin; //, *app_name_temp;
        size_t diff;

        if (all_arguments == NULL || app_name == NULL) {
            return;
        }

        full_path = (char*)all_arguments + sizeof(int);

        app_end = strcasestr(full_path, ".app");
        if (app_end == NULL) {
            app_begin = strrchr(full_path, '/');
            if (app_begin != NULL)
                *app_name = strdup(app_begin+1);
            else
                *app_name = strdup(full_path);
        } else {
            app_begin = app_end;
            while (*(--app_begin) != '/') {}
            diff = app_end - app_begin;
            *app_name = malloc(diff);         
            strncpy(*app_name, app_begin+1, diff-1);
        }
    }

请注意，您的代码存在内存泄漏。 extract_app_name 的调用者应在使用完字符串后释放该字符串。