Hi,
On Tue, Jan 13, 2009 at 10:51 AM, Henrik Austad <henrik@xxxxxxxxx> wrote:> I'm using gettimeofday to get the most accurate time from the kernel>> When I use calloc to create and initalize memory for the struct timeval *tv,> everything works fine:>> struct timeval *tv;> tv = (struct timeval *)calloc(1, sizeof(struct timeval));> if (!tv) {> /* handle error... */> exit> }> gettimeofday(tv);according http://dell5.ma.utexas.edu/cgi-bin/man-cgi?gettimeofday+2gettimeofday has 2 input agruments.I get you code and compile and works ok for both (mallo, calloc).My source code:
#include <stdio.h>#include <stdlib.h>#include <sys/time.h>/* * struct timeval { * time_t tv_sec; * suseconds_t tv_usec; * }; */
void gettime_1(void){ struct timeval *tv; tv = (struct timeval *)malloc(sizeof (*tv)); if (!tv) { fprintf(stderr, "Could not allocate memory for timestruct\n"); return; } gettimeofday(tv, NULL); printf("Time1: %lu, %lu\n", (long unsigned)tv->tv_sec, (longunsigned)tv->tv_usec);}void gettime_2(void){ struct timeval *tv; tv = (struct timeval *)calloc(1,sizeof (*tv)); if (!tv) { fprintf(stderr, "Could not allocate memory for timestruct\n"); return; } gettimeofday(tv, NULL); printf("Time2: %lu, %lu\n", (long unsigned)tv->tv_sec, (longunsigned)tv->tv_usec);}int main (int argc, char *argv[]){ gettime_1(); gettime_2(); return 0;}
>> But, when I use malloc, gettimeofday segfaults, even though tv != NULL, and I> can set tv_sec and tv_usec manually without getting a segfault. Normally I'm> able to figure these kind of things out, but right now, I'm stuck. Especially> as it works if I use calloc and gettimeofday on a separate struct, or, if i> print the address of the malloc'ed timeval.>> strace of program:>> execve("./test_time", ["./test_time"], [/* 49 vars */]) = 0> brk(0) = 0x2330000> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) => 0x7f42ca271000> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or> directory)> mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) => 0x7f42ca26f000> access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or> directory)> open("tls/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or> directory)> open("tls/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or> directory)> open("x86_64/libc.s#include <stdio.h>> #include <stdlib.h>>> /*> * struct timeval {> * time_t tv_sec;> * suseconds_t tv_usec;> * };> */>> void gettime_1(void)> {> struct timeval *tv;> tv = (struct timeval *)malloc(1*sizeof (struct timeval));> if (!tv) {> fprintf(stderr, "Could not allocate memory for timestruct\n");> return;> }> gettimeofday(tv);> printf("Time1: %lu, %lu\n", (long unsigned)tv->tv_sec, (long unsigned)tv->>tv_usec);> }> void gettime_2(void)> {> struct timeval *tv;> tv = (struct timeval *)calloc(1,sizeof (struct timeval));> if (!tv) {> fprintf(stderr, "Could not allocate memory for timestruct\n");> return;> }> gettimeofday(tv);> printf("Time2: %lu, %lu\n", (long unsigned)tv->tv_sec, (long unsigned)tv->>tv_usec);> }> int main (int argc, char *argv[])> {> gettime_1();> gettime_2();> return 0;> }> o.6", O_RDONLY) = -1 ENOENT (No such file or directory)> open("libc.so.6", O_RDONLY) = -1 ENOENT (No such file or> directory)> open("/usr/lib32/tls/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or> directory)> stat("/usr/lib32/tls/x86_64", 0x7fffd226fb20) = -1 ENOENT (No such file or> directory)> open("/usr/lib32/tls/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or> directory)> stat("/usr/lib32/tls", 0x7fffd226fb20) = -1 ENOENT (No such file or> directory)> open("/usr/lib32/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or> directory)> stat("/usr/lib32/x86_64", 0x7fffd226fb20) = -1 ENOENT (No such file or> directory)> open("/usr/lib32/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or> directory)> stat("/usr/lib32", {st_mode=S_IFDIR|0755, st_size=36864, ...}) = 0> open("/etc/ld.so.cache", O_RDONLY) = 3> fstat(3, {st_mode=S_IFREG|0644, st_size=115573, ...}) = 0> mmap(NULL, 115573, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f42ca252000> close(3) = 0> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or> directory)> open("/lib/libc.so.6", O_RDONLY) = 3> read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\220\345"..., 832) => 832> fstat(3, {st_mode=S_IFREG|0755, st_size=1502520, ...}) = 0> mmap(NULL, 3609304, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) => 0x7f42c9ce2000> mprotect(0x7f42c9e4b000, 2093056, PROT_NONE) = 0> mmap(0x7f42ca04a000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|> MAP_DENYWRITE, 3, 0x168000) = 0x7f42ca04a000> mmap(0x7f42ca04f000, 17112, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|> MAP_ANONYMOUS, -1, 0) = 0x7f42ca04f000> close(3) = 0> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) => 0x7f42ca251000> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) => 0x7f42ca250000> arch_prctl(ARCH_SET_FS, 0x7f42ca2506e0) = 0> mprotect(0x7f42ca04a000, 16384, PROT_READ) = 0> mprotect(0x600000, 4096, PROT_READ) = 0> mprotect(0x7f42ca272000, 4096, PROT_READ) = 0> munmap(0x7f42ca252000, 115573) = 0> brk(0) = 0x2330000> brk(0x2351000) = 0x2351000> --- SIGSEGV (Segmentation fault) @ 0 (0) ---> +++ killed by SIGSEGV +++> Process 9387 detached>>> The program itself (note the usage of gettime_1 and gettime_2 (if I call> gettime_2 before gettime_1, it works, if I call gettime_1 first, it> segfaults).>> #include <stdio.h>> #include <stdlib.h>>> /*> * struct timeval {> * time_t tv_sec;> * suseconds_t tv_usec;> * };> */>> void gettime_1(void)> {> struct timeval *tv;> tv = (struct timeval *)malloc(1*sizeof (struct timeval));> if (!tv) {> fprintf(stderr, "Could not allocate memory for timestruct\n");> return;> }> gettimeofday(tv);> printf("Time1: %lu, %lu\n", (long unsigned)tv->tv_sec, (long unsigned)tv->>tv_usec);> }> void gettime_2(void)> {> struct timeval *tv;> tv = (struct timeval *)calloc(1,sizeof (struct timeval));> if (!tv) {> fprintf(stderr, "Could not allocate memory for timestruct\n");> return;> }> gettimeofday(tv);> printf("Time2: %lu, %lu\n", (long unsigned)tv->tv_sec, (long unsigned)tv->>tv_usec);> }> int main (int argc, char *argv[])> {> gettime_1();> gettime_2();> return 0;> }>>> Any help appreciated :-)>> --> Henrik>> --> To unsubscribe from this list: send an email with> "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx> Please read the FAQ at http://kernelnewbies.org/FAQ>>
-- as simple as primitive as possible----------------------------------------------Marek Beliško - open-nandraRuská Nová Ves 21908005 PrešovSlovakiahttp://open-nandra.com��.n��������+%����w�j)p���{.n����z�ޖw�n'���q���b�������v��m�����Y�����
