C
如何在應用程序啟動時避免多次“libFoo.so”open() 呼叫？
我在*/UNI/System/Libs/libmbedcrypto.so.3目錄中有下一個 so 文件。當我啟動我的應用程序時，使用libmbedcrypto.so.3*和strace我看到：
open("/UNI/System/Libs/tls/v7l/neon/vfp/libmbedcrypto.so.3", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) stat64("/UNI/System/Libs/tls/v7l/neon/vfp", 0x7ef80610) = -1 ENOENT (No such file or directory) open("/UNI/System/Libs/tls/v7l/neon/libmbedcrypto.so.3", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) stat64("/UNI/System/Libs/tls/v7l/neon", 0x7ef80610) = -1 ENOENT (No such file or directory) open("/UNI/System/Libs/tls/v7l/vfp/libmbedcrypto.so.3", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) stat64("/UNI/System/Libs/tls/v7l/vfp", 0x7ef80610) = -1 ENOENT (No such file or directory) open("/UNI/System/Libs/tls/v7l/libmbedcrypto.so.3", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) //... more stat64 & open open("/UNI/System/Libs/libmbedcrypto.so.3", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) stat64("/UNI/System/Libs", {st_mode=S_IFDIR|0777, st_size=4096, ...}) = 0如何擺脫所有 open 和 stat64 呼叫？
**這很正常。**如果不從頭開始在彙編中重寫程序，或者編寫自己的 C 庫來配合它，您實際上無法擺脫這種情況。這幾乎是任何程序的標準。說真的，你不需要優化像這樣無關緊要的東西。嘗試訪問不存在的文件所浪費的時間可以忽略不計，正如您在下面的系統呼叫跟踪中看到的那樣
true，該程序旨在從嵌入式系統返回 0：root@UP-1044:~# strace -T -e trace=open true open("/tmp/t/usr/lib/libgcc_s.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory) <0.000643> open("/tmp/t/lib/libgcc_s.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory) <0.000861> open("/lib/libgcc_s.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3 <0.000208> +++ exited with 0 +++在每個系統呼叫上浪費的時間似乎不到一毫秒！