我有几个文件正在尝试在Ubuntu中使用gcc进行编译。我有vmware机器16.04 ubuntu，它是64位计算机。我在makefile中添加了用于32位编译的标志。 （-m32标志）。
这是makefile：
request": "GET https://www.vvvvvvv HTTP/2.0""
http_method": "GET"
我尝试编译代码失败，因为我收到以下错误：
all: clean binsem.a ut.a ph
FLAGS = -Wall -L./ -m32
ph: ph.c
gcc ${FLAGS} ph.c -lbinsem -lut -o ph
binsem.a:
gcc $(FLAGS) -c binsem.c
ar rcu libbinsem.a binsem.o
ranlib libbinsem.a
ut.a:
gcc $(FLAGS) -c ut.c
ar rcu libut.a ut.o
ranlib libut.a
clean:
rm -f *.o
rm -f a.out
rm -f *~
rm -f ph
rm -f *a
**我尝试过-**
文件“ ph.c”是以下文件-
ph.c:126:12: warning: ‘main’ defined but not used [-Wunused-function]
/usr/lib/gcc/i686-linux-gnu/5/../../../i386-linux-gnu/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: error: ld returned 1 exit status
Makefile:6: recipe for target 'ph' failed
make: *** [ph] Error 1
makefile还会尝试编译这些文件-#include <stdio.h>
#include <setjmp.h>
#include <signal.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <stdint.h>
#include <sys/time.h>
#include <inttypes.h>
#include "binsem.h"
#include "ut.h"
#define LEFT (i+N-1)%N
#define RIGHT (i+1)%N
#define THINKING 0
#define HUNGRY 1
#define EATING 2
int N;
volatile int *phil_state;
sem_t *s;
sem_t mutex;
int *tid;
uint64_t get_wall_time() {
struct timeval time;
gettimeofday(&time, NULL);
uint64_t millis = (time.tv_sec * (uint64_t)1000) + (time.tv_usec / 1000);
return millis;
}
void think(int p) {
int i, factor;
volatile int j;
printf("Philosopher (%d) - time %" PRId64 " - is thinking\n",p, get_wall_time()); fflush (stdout);
factor = 1 + random()%5;
for (i = 0; i < 100000000*factor; i++){
j += (int) i*i;
}
printf("Philosopher (%d) - time %" PRId64 " - is hungry\n", p, get_wall_time()); fflush (stdout);
}
void eat(int p){
int i, factor;
volatile int j;
printf("Philosopher (%d) - time %" PRId64 " - is eating\n",p, get_wall_time()); fflush (stdout);
factor = 1 + random()%5;
for (i = 0; i < 100000000*factor; i++){
j += (int) i*i;
}
//printf("Philosopher (%d) - time %" PRId64 " - is thinking\n",p, get_wall_time()); fflush (stdout);
}
void test(int i){
if (phil_state[i] == HUNGRY &&
phil_state[LEFT] != EATING &&
phil_state[RIGHT] != EATING){
phil_state[i] = EATING;
binsem_up(&(s[i]));
}
}
void take_forks(int i){
binsem_down(&mutex);
phil_state[i] = HUNGRY;
test(i);
binsem_up(&mutex);
binsem_down(&(s[i]));
}
void put_forks(int i){
binsem_down(&mutex);
phil_state[i] = THINKING;
test(LEFT);
test(RIGHT);
binsem_up(&mutex);
}
void int_handler(int signo) {
long int duration;
int i;
for (i = 0; i < N; i++) {
duration = ut_get_vtime(tid[i]);
printf("Philosopher (%d) used the CPU %ld.%ld sec.\n",
i+1,duration/1000,duration%1000);
}
exit(0);
}
void philosopher(int i){
while (1){
think(i);
take_forks(i);
eat(i);
put_forks(i);
}
}
static int main(int argc, char *argv[])
{
int c;
if (argc != 2){
printf("Usage: %s N\n", argv[0]);
exit(1);
}
N = atoi(argv[1]);
if (N < 2){
printf("Usage: %s N (N >=2)\n", argv[0]);
exit(1);
}
ut_init(N);
s = (sem_t *)malloc (N * sizeof(sem_t));
phil_state = (int *) malloc (N * sizeof(int));
tid = (int *) malloc (N * sizeof(int));
for (c = 0; c < N ; c++){
phil_state[c] = THINKING;
binsem_init(&(s[c]), 0);
}
for (c = 0; c < N ; c++){
tid[c] = ut_spawn_thread(philosopher,c);
printf("Spawned thread #%d\n", tid[c]);
}
binsem_init(&mutex, 1);
signal(SIGINT,int_handler);
ut_start();
return 0; // avoid warnings
}
，ut.c
binsem.cbinsem.c
#include <stdlib.h>
#ifndef _UT_H
#define _UT_H
#include "ut.h"
#include <sys/time.h> // for itimerval
#include <unistd.h> // for alarm
#include <stdlib.h> // for malloc
#include <stdio.h> // for perror
#include <ucontext.h>
# include "ut.h"
#define MAX_TAB_SIZE 128 // the maximal threads table size.
#define MIN_TAB_SIZE 2 // the minimal threads table size.
#define SYS_ERR -1 // system-related failure code
#define TAB_FULL -2 // full threads table failure code
/*This type defines a single slot (entry) in the threads table. Each slot describes a single
thread. Note that we don't need to keep the thread state since every thread is always ready
or running. We also don't have to support adding/stopping thread dynamically, so we also don't
have to manage free slots.*/
typedef struct ut_slot {
ucontext_t uc;
unsigned long vtime; /* the CPU time (in milliseconds) consumed by this thread.*/
void (*func)(int); /* the function executed by the thread.*/
int arg; /* the function argument.*/
} ut_slot_t, *ut_slot;
static ut_slot threads; // pointer to thread table
static volatile int numThreads = 0; // number of threads in the table
static volatile int currentThread = 0; // current thread
static ucontext_t mainThread;
#define STACKSIZE 8192 // the thread stack size.
/* The TID (thread ID) type. TID of a thread is actually the index of the thread in the
threads table. */
typedef short int tid_t;
void handler(int signal){
alarm(1); //the alarm every second as demanded in the assignment
currentThread = (currentThread +1 ) % numThreads;
printf("in signal handler: switching from %d to %d\n", currentThread, currentThread - 1);
swapcontext(&threads[currentThread].uc, &threads[currentThread].uc); /*save current thread,
* load next thread*/
if (signal == SIGVTALRM){ // increment the time stats
threads[currentThread].vtime+=100;
} else if(signal==SIGALRM) {
if (swapcontext(&threads[currentThread - 1].uc, &threads[currentThread].uc) == -1) {
perror("could not do swapping");
exit(1);
}
}
}
int ut_init(int tab_size){
/// (###)
if(tab_size < MAX_TAB_SIZE) {
threads = (ut_slot) malloc(tab_size * sizeof(int(ut_slot_t)));
}
else{
threads = (ut_slot) malloc(MAX_TAB_SIZE * sizeof(int(ut_slot_t)));
}
if (!threads) {
return SYS_ERR;
}
return 0;
}
tid_t ut_spawn_thread(void (*func)(int), int arg){
/*uc[1].uc_link = &uc[0];
uc[1].uc_stack.ss_sp = st1; //stack fro thread 1
uc[1].uc_stack.ss_size = sizeof st1; //size of stack for therad
makecontext(&uc[1], (void(*)(void)) f, 1, 1); */
int thread_stack_size = STACKSIZE/8; //no need for 8K in size
if (numThreads>=TAB_FULL){ //(*)
return TAB_FULL;
}
if (getcontext(&threads[numThreads].uc)==-1){
return SYS_ERR;
}
ut_slot_t newThread;
threads[numThreads] = newThread;
threads[numThreads].uc.uc_link = &mainThread;
threads[numThreads].uc.uc_stack.ss_sp = (void* *)malloc(thread_stack_size);
if(threads[numThreads].uc.uc_stack.ss_sp==NULL){
return SYS_ERR;
}
makecontext(&threads[numThreads].uc,(void(*)(void))func,1,arg);
numThreads++;
return numThreads - 1;
}
int ut_start(void){
struct sigaction sigaction1;
int firstThread = 0; /*represents the current thread*/
struct itimerval itv;
/* set up vtimer for accounting */
itv.it_interval.tv_sec = 0;
itv.it_interval.tv_usec = 10000;
itv.it_value = itv.it_interval;
/* Initialize the data structures for SIGALRM handling. */
sigaction1.sa_flags = SA_RESTART; //restart instead of throwing exception
sigfillset(&sigaction1.sa_mask); // don't throw exception for additional signals
sigaction1.sa_handler = handler; // specify handler for the sigaction declared
if (sigaction(SIGVTALRM, &sigaction1, NULL) < 0)
return SYS_ERR;
/*START THE TIMER */
if (setitimer(ITIMER_VIRTUAL, &itv, NULL) < 0)
return SYS_ERR;
if (sigaction(SIGINT, &sigaction1, NULL) < 0)
return SYS_ERR;
/* Start running. */
alarm(1); //alarm every second
if(swapcontext(&threads[firstThread].uc,&threads[firstThread+1].uc)==-1){ //swap first time
return SYS_ERR;
}
return -1;
}
unsigned long ut_get_vtime(tid_t tid){
return threads[tid].vtime;
}
#endif
有什么想法吗？
答案 0 :(得分：2)
您将main函数声明为static。这意味着它将具有 内部 linkage，并且不会导出。因此，链接器将无法找到它。
删除static修饰符，应该可以。
不过，您的Makefile中还有许多其他问题很可能会导致问题：
目标ph仅 取决于ph.c，而不取决于您要链接的库。您还需要添加库作为依赖项（它们的完整文件名）。
还应该使库依赖于用于创建它们的目标文件，并依赖隐式规则从源文件构建目标文件。
还要注意，对于名为A的库，文件名必须为libA.a，否则链接器将无法使用-l找到它（小写） L）选项。
答案 1 :(得分：2)
错误消息很清楚：
(.text+0x18): undefined reference to `main'
在 ph.c 中（可能是 Java 习惯的？）：
static int main(int argc, char *argv[])
在 C 中：
静态（[CPPReference]: C keywords: static）表示内部链接（仅在当前的翻译单元（ ph .o ）），因此 linker （ loader ）不会“看到” static 符号
链接到应用程序（不是动态库或共享对象（ .so ：与{{1} }）），必须显式定义 main ，并且 linker
上述2种方法的结合会带来您所遇到的问题。
删除 静态 ，就可以了。
注意： makefile 中可能还有其他错误。