clock_gettime和CLOCK_MONOTONIC上的编译错误

我在程序中使用clock_gettime。 我试过包括但是没有效果。 我还为我的编译器参数添加了-lrt但仍然得到了相同的错误。

这是开启

CentOS Linux release 7.2.1511 (Core) gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-4) GNU ld version 2.23.52.0.1-55.el7 20130226 ldd (GNU libc) 2.17 

编译器输出：

 gcc -o main packet.c connect.c transport.c accept.c main.c close.c util.c receive.c send.c congestion.c -Wall -g -std=c99 -lrt util.c: In function 'millis': util.c:42:21: error: storage size of 't' isn't known struct timespec t; ^ util.c:43:5: warning: implicit declaration of function 'clock_gettime' [-Wimplicit-function-declaration] clock_gettime(CLOCK_MONOTONIC_RAW, &t); ^ util.c:43:19: error: 'CLOCK_MONOTONIC_RAW' undeclared (first use in this function) clock_gettime(CLOCK_MONOTONIC_RAW, &t); ^ 

Makefile文件

 CFLAGS = -Wall -g -std=c99 LIBS = -lrt # Should be equivalent to your list of C files, if you don't build selectively SRC=$(wildcard *.c) main: $(SRC) gcc -o $@ $^ $(CFLAGS) $(LIBS) 

util.h的顶部

 #ifndef UTILS_438_H_ #define UTILS_438_H_ #include "const.h" #include "data.h" #include "transport.h" #include  

util.c的顶部

 #include "util.h" #include  #include  #include  

如果我能提供更多信息以帮助解答这个问题，请告诉我

Answer 1

在包含标题（ ）之前，请执行

 #define _POSIX_C_SOURCE 199309L 

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http://man7.org/linux/man-pages/man2/clock_gettime.2.html

glibc的function测试宏要求（参见feature_test_macros（7））：

  clock_getres(), clock_gettime(), clock_settime(): _POSIX_C_SOURCE >= 199309L 

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http://man7.org/linux/man-pages/man7/feature_test_macros.7.html

_POSIX_C_SOURCE定义此宏会导致头文件公开定义，如下所示：

  · The value 1 exposes definitions conforming to POSIX.1-1990 and ISO C (1990). · The value 2 or greater additionally exposes definitions for POSIX.2-1992. · The value 199309L or greater additionally exposes definitions for POSIX.1b (real-time extensions). · The value 199506L or greater additionally exposes definitions for POSIX.1c (threads). · (Since glibc 2.3.3) The value 200112L or greater additionally exposes definitions corresponding to the POSIX.1-2001 base specification (excluding the XSI extension). This value also causes C95 (since glibc 2.12) and C99 (since glibc 2.10) features to be exposed (in other words, the equivalent of defining _ISOC99_SOURCE). · (Since glibc 2.10) The value 200809L or greater additionally exposes definitions corresponding to the POSIX.1-2008 base specification (excluding the XSI extension).