NSLog日志输出不全问题分析与解决方案-阿里云开发者社区

NSLog日志输出不全问题分析与解决方案

2024-05-23 194

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简介： NSLog日志输出不全问题分析与解决方案

采用NSLog打印超长的字符串，可能出现日志没有打印完全，后面一部分丢失了。

开始以为是和异步一致一起打印时被异步日志线程强行插入，结果找了半天没有找到，说明它根本没有打印出来。

出问题的日志打印代码：NSLog(@"3加密前：%@", data);，怎么看这个代码没有任何问题，打印（NSLog(@"data.length:%d", data.length);）出的这个字符串长度是比较长：data.length:7353。我怀疑是系统这个打印函数是有内存限制，超过它的长度就直接截取扔掉了后面的字符。

分析它最大能支持多长的字符串：加[ { "openType" : "03", "openTime" : "1564651163", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651170", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651176", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651182", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651188", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651194", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651200", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651206", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651212", "uid" : "3130303030393539" }, { "openType" : "03", "openTime" : "1564651218", "uid" : "3130303030393539" }, { "openType" : "03", "ope，它实际只有1021个包含空格汉字的字符。难道它真的只能打印这么一点字符串吗？

我直接对这个字符串打印：NSLog(@"%@", data);。结果直接把这7353个字符全部打印出来了。可以看到它不是只打印这1021个汉字和字符这么点内容，应该可以打印很多。

难道是因为拼接的同时进行打印才有这个限制，我测试这种情况：NSLog(@"testdata%@", data);，结果仍是可以把这7353个字符全部打印出来。可以看出推测不完全对。

然后我试一下再外面拼接字符串，直接对字符串进行打印：

                str = [NSString stringWithFormat:@"加%@", data];
                NSLog(@"%@", str);

结果和不行，也把这7353个字符全部打印出来。可以看出推测不完全对。

比对他们的不同发现了规律：在打印是拼接字符串，并且里面的常量字符串里有中文，才会出现打印的字符串很短，超过最大的长度字符串后面的部分被扔掉。那么找到的问题的所在，那来研究下这个最大长度是多少呢？

由于发现打印的最大的字符串最大是1021个字符，包含一个汉字，很可能和1021个字符有关，就对字符串进行截取测试。测试发现：在一个中文常量的情况下，和一个1020个字符的字符串拼接没有问题，但是和1021个字符的字符串拼接后打印少了最后一个字符。

总结：

当直接打印一个长字符串，只要不是超级长，一般没有问题。当加入输出信息，并且有常量中文时，和变量字符串拼接时，当他们的字符数和超过1021时，后面的字符串打印不出来（测试的场景是：一个中文字符和和不含有非汉字json字符串。若中文多，他们的总和是否为1021，没有进一步研究）。

开发环境有效的重置NSLog的方法，这种方案我提倡，这个已经原来的mac的控制台打印函数，而是采用的linux操作系统日志函数进行替换了原来的函数了：

#ifndef __OPTIMIZE__
    //这里执行的是debug模式下，打印日志，当前行
    #define NSLog(...) printf("%s %s 第%d行: %s\n",__TIME__, __PRETTY_FUNCTION__ ,__LINE__, [[NSString stringWithFormat:__VA_ARGS__] UTF8String]);
#else
        //这里执行的是release模式下，不打印日志
    #define NSLog(...)
#endif

推荐解决方案：

先把要打印的所有字符串拼接为一个字符串，然后一次打印。

解决方案：

先把要打印的所有字符串拼接为一个字符串，然后一次打印。至于直接重置NSLog：#define NSLog(format, ...) printf("TIME:%s FILE:%s(%d行) FUNCTION:%s \n %s\n\n",__TIME__, [[[NSString stringWithUTF8String:__FILE__] lastPathComponent] UTF8String], __LINE__, __PRETTY_FUNCTION__, [[NSString stringWithFormat:(format), ##__VA_ARGS__] UTF8String])我不提倡。

测试代码：

                NSLog(@"data.length:%d", data.length);
                NSString *str = [NSString stringWithFormat:@"%@", [data substringToIndex:1022]];
                NSLog(@"加%@", str);
                NSLog(@"str.length:%d", str.length);
                str = [NSString stringWithFormat:@"%@", [data substringToIndex:1021]];
                NSLog(@"加%@", str);
                str = [NSString stringWithFormat:@"加%@", [data substringToIndex:1021]];
                NSLog(@"%@", str);
                NSLog(@"str.length:%d", str.length);
                str = [NSString stringWithFormat:@"%@", [data substringToIndex:1020]];
                NSLog(@"加%@", str);
                str = [NSString stringWithFormat:@"加%@", [data substringToIndex:1020]];
                NSLog(@"%@", str);
                NSLog(@"str.length:%d", str.length);
//                str = [NSString stringWithFormat:@"3加密前：data:%@", data];
                NSLog(@"3加密前：%@", data);

打印的日志，大家可以对照进行分析：

2019-08-02 16:11:54.297359+0800 ELock[1447:400407] data.length:7353
2019-08-02 16:11:54.297597+0800 ELock[1447:400407] 加[    {       "openType" : "03",      "openTime" : "1564651163",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651170",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651176",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651182",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651188",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651194",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651200",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651206",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651212",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "openTime" : "1564651218",      "uid" : "3130303030393539"   },     {       "openType" : "03",      "ope
2019-08-02 16:11:54.461804+0800 ELock[1447:400407] str.length:1022
2019-08-02 16:11:54.461982+0800 ELock[1447:400407] 加[    {       "openType" : "03",      "openTime" : "1564651163",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651170",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651176",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651182",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651188",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651194",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651200",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651206",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651212",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651218",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "ope
2019-08-02 16:11:54.473584+0800 ELock[1447:400407] 加[    {       "openType" : "03",      "openTime" : "1564651163",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651170",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651176",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651182",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651188",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651194",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651200",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651206",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651212",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651218",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "open
2019-08-02 16:11:54.475564+0800 ELock[1447:400407] str.length:1022
2019-08-02 16:11:54.475860+0800 ELock[1447:400407] 加[    {       "openType" : "03",      "openTime" : "1564651163",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651170",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651176",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651182",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651188",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651194",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651200",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651206",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651212",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651218",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "ope
2019-08-02 16:11:54.477939+0800 ELock[1447:400407] 加[    {       "openType" : "03",      "openTime" : "1564651163",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651170",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651176",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651182",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651188",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651194",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651200",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651206",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651212",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "openTime" : "1564651218",      "uid" : "3420303038763539"   },     {       "openType" : "03",      "ope
2019-08-02 16:11:54.480312+0800 ELock[1447:400407] str.length:1021

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NSLog日志输出不全问题分析与解决方案

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