I have gone through similar questions and seen answers given, where given and none of those points me to what I am doing wrong. I keep getting undefined reference to 'concatf' while the function is properly defined in the header file.
concatf.c
#include "concatf.h"
/*
* vscprintf:
* MSVC implements this as _vscprintf, thus we just 'symlink' it here
* GNU-C-compatible compilers do not implement this, thus we implement it here
*/
#ifdef _MSC_VER
#define vscprintf _vscprintf
#endif
#ifdef __GNUC__
int vscprintf(const char *format, va_list ap)
{
va_list ap_copy;
va_copy(ap_copy, ap);
int retval = vsnprintf(NULL, 0, format, ap_copy);
va_end(ap_copy);
return retval;
}
#endif
int vasprintf(char **strp, const char *format, va_list ap)
{
int len = vscprintf(format, ap);
if (len == -1)
return -1;
char *str = (char*)malloc((size_t) len + 1);
if (!str)
return -1;
int retval = vsnprintf(str, len + 1, format, ap);
if (retval == -1) {
free(str);
return -1;
}
*strp = str;
return retval;
}
int concatf(char **strp, const char *format, ...)
{
va_list ap;
va_start(ap, format);
int retval = vasprintf(strp, format, ap);
va_end(ap);
return retval;
}
concatf.h
#ifndef CONCATF_H
#define CONCATF_H
#if defined(__GNUC__) && ! defined(_GNU_SOURCE)
#define _GNU_SOURCE /* needed for (v)asprintf, affects '#include <stdio.h>' */
#endif
#include <stdio.h> /* needed for vsnprintf */
#include <stdlib.h> /* needed for malloc, free */
#include <stdarg.h> /* needed for va_* */
int concatf(char **strp, const char *format, ...);
#endif // CONCATF_H
build.c
#include "concatf.h"
#include <stdio.h>
#include <stdlib.h>
extern char _binary_script_php_start;
extern char _binary_script_php_end;
int main(int argc, char *argv[]) {
// EXTRACT OUR RESOURCE OBJECT INTO /tmp/test.php
char *p = &_binary_script_php_start;
FILE *fp = fopen("/tmp/test.php","wb");
while ( p != &_binary_script_php_end ) {
fputc(*p++,fp);
}
fclose(fp);
// NOW READ IN OUR STANDARD ARGUMENTS AND LAUNCH OUR COMMAND
int i = 1;
char *cmd = "php /tmp/test.php";
char *s = NULL;
// asprintf(&s, "%s",cmd);
// for(i = 1; i < argc; i++) {
// asprintf(&s, "%s \"%s\"",s,argv[i]);
// }
// concatf("%s",cmd);
// for(i = 1; i < argc; i++) {
// concatf("%s \"%s\"",s,argv[i]);
// }
concatf(&s, "%s",cmd);
for(i = 1; i < argc; i++) {
concatf(&s, "%s \"%s\"",s,argv[i]);
}
system(s);
free(s);
unlink("/tmp/test.php"); // comment me out for debugging if you want
}
These codes run on my environment but fail to run on the second windows environment and those of my colleagues, I can't seem to point why that is the case.
To run it you will need a php file named script.php run ld -r -b binary script.php data.o to complie your php file and gcc build.c data.o -o runme to link the php file with the build function. You can find the sample project here https://github.com/Sammiiie/C_php_http.
Related
I am trying to create a shared library in Linux. How can I pass an argument to function my_load() when library is loaded? In my C application, I make a call to test_func() then it automatically executes my_load() first before the called function then lastly it executes my_unload()
#include <stdio.h>
void __attribute__ ((constructor)) my_load(int argc, char *argv[]);
void __attribute__ ((destructor)) my_unload(void);
void test_func(void);
void my_load(int argc, char *argv[]) {
printf("my_load: %d\n", argc);
}
void my_unload(void) {
printf("my_unload\n");
}
void test_func(void) {
printf("test_func()\n");
}
Your dynamic library can always read /proc/self/cmdline to see what the command-line parameters used to execute the current executable are. example.c:
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
static char **get_argv(int *const argcptr)
{
char **argv;
char *data = NULL;
size_t size = 0; /* Allocated to data */
size_t used = 0;
size_t argc, i;
ssize_t bytes;
int fd;
if (argcptr)
*argcptr = 0;
do {
fd = open("/proc/self/cmdline", O_RDONLY | O_NOCTTY);
} while (fd == -1 && errno == EINTR);
if (fd == -1)
return NULL;
while (1) {
if (used >= size) {
char *old_data = data;
size = (used | 4095) + 4096;
data = realloc(data, size + 1);
if (data == NULL) {
free(old_data);
close(fd);
errno = ENOMEM;
return NULL;
}
}
do {
bytes = read(fd, data + used, size - used);
} while (bytes == (ssize_t)-1 && errno == EINTR);
if (bytes < (ssize_t)0) {
free(data);
close(fd);
errno = EIO;
return NULL;
} else
if (bytes == (ssize_t)0)
break;
else
used += bytes;
}
if (close(fd)) {
free(data);
errno = EIO;
return NULL;
}
/* Let's be safe and overallocate one pointer here. */
argc = 1;
for (i = 0; i < used; i++)
if (data[i] == '\0')
argc++;
/* Reallocate to accommodate both pointers and data. */
argv = realloc(data, (argc + 1) * sizeof (char *) + used + 1);
if (argv == NULL) {
free(data);
errno = ENOMEM;
return NULL;
}
data = (char *)(argv + argc + 1);
memmove(data, argv, used);
/* In case the input lacked a trailing NUL byte. */
data[used] = '\0';
/* Assign the pointers. */
argv[0] = data;
argc = 0;
for (i = 0; i < used; i++)
if (data[i] == '\0')
argv[++argc] = data + i + 1;
/* Final pointer points to past data. Make it end the array. */
argv[argc] = NULL;
if (argcptr)
*argcptr = (int)argc;
return argv;
}
/* Example standard error functions, that avoid the use of stdio.h.
*/
static void wrerr(const char *p)
{
if (p != NULL) {
const char *const q = p + strlen(p);
ssize_t n;
while (p < q) {
n = write(STDERR_FILENO, p, (size_t)(q - p));
if (n > (ssize_t)0)
p += n;
else
if (n != (ssize_t)-1)
return;
else
if (errno != EINTR)
return;
}
}
}
static void wrerrint(const int i)
{
char buffer[32];
char *p = buffer + sizeof buffer;
unsigned int u;
if (i < 0)
u = (unsigned int)(-i);
else
u = (unsigned int)i;
*(--p) = '\0';
do {
*(--p) = '0' + (u % 10U);
u /= 10U;
} while (u > 0U);
if (i < 0)
*(--p) = '-';
wrerr(p);
}
static void init(void) __attribute__((constructor));
static void init(void)
{
int argc, i, saved_errno;
char **argv;
saved_errno = errno;
argv = get_argv(&argc);
if (argv == NULL) {
const char *const errmsg = strerror(errno);
wrerr("libexample.so: get_argv() failed: ");
wrerr(errmsg);
wrerr(".\n");
errno = saved_errno;
return;
}
for (i = 0; i < argc; i++) {
wrerr("libexample.so: argv[");
wrerrint((int)i);
wrerr("] = '");
wrerr(argv[i]);
wrerr("'\n");
}
free(argv);
errno = saved_errno;
return;
}
Compile using e.g.
gcc -Wall -fPIC -shared example.c -ldl -Wl,-soname,libexample.so -o libexample.so
and test using e.g.
LD_PRELOAD=./libexample.so /bin/echo foo bar baz baaz
(Note that plain echo is a shell built-in, and you need to execute another binary like /bin/echo to load the preload library.)
However, most dynamic libraries take arguments in environment variables instead; for example, YOURLIB_MEM for some memory size hint, or YOURLIB_DEBUG for enabling verbose debugging output during runtime.
(My example code does not use stdio.h output, because not all binaries use it, especially if written in some other language. Instead, the wrerr() and wrerrint() are small stupid helper functions that use low-level unistd.h I/O to write directly to standard error; this always works, and causes minimal side effects at run time.)
Questions?
You can't.
__attribute__((constructor)) simply doesn't support this.
There doesn't seem to be any reason you can't just call my_load(argc, argv) at the very beginning of main().
You can use atexit to register a function to be called when your program exits normally, or returns from main.
int main(int argc, char **argv)
{
my_load(argc, argv);
atexit(my_unload);
// ...
}
AFAIK, there is no way to pass arguments to gcc constructor and destructor functions. The best you can do is to use global variables.
In you example, you could try :
In main :
int Argc;
char *Argv[];
int main(int argc, char *argv[]) {
Argc = argc;
Argv = argv;
...
}
In shared library :
extern int Argc;
...
void __attribute__ ((constructor)) my_load();
...
void my_load() {
printf("my_load: %d\n", Argc);
}
But anyway, it can only work if you explicitely load the shared library through dlopen. It it is directly referenced at link time, the constructor function will be called before first instruction in main and you will always find the original value or 0 in Argc.
Sorry to resurrect an oldie here but I just tested this on both Linux and Mac OS:
$ gcc -x c -o test_prog -
#include <stdio.h>
void __attribute__ ((constructor)) my_load(int argc, char *argv[]);
void __attribute__ ((destructor)) my_unload(void);
void test_func(void);
void my_load(int argc, char *argv[]) {
printf("my_load: %d\n", argc);
}
void my_unload(void) {
printf("my_unload\n");
}
void test_func(void) {
printf("test_func()\n");
}
int main() { return 0; }
And it prints this result on both systems:
$ ./test_prog foo bar baz
my_load: 4
my_unload
In order for it to work as a shared library I did have to add the linker option -Wl,--no-gc-sections because it otherwise aggressively removed the constructor & destructor. But otherwise yeah this works already.
This doesn’t use the __attribute__ ((constructor)) syntax, but if you specify a custom _init function, you can do so:
// foo.c
#include <stdio.h>
void my_constructor(int argc, char**argv) {
printf("my_constructor init: %s\n", argv[1]);
}
To do so you need to pass ld -init my_constructor or gcc -Wl,-init,my_constructor, e.g.
gcc foo.c -shared -o libfoo.so -Wl,-init,my_constructor
I need to generate three different types of paths on runtime:
/sys/class/gpio/gpio%d
/sys/class/gpio/gpio%d/value
/sys/class/gpio/gpio%d/direction
Currently I generate these by doing the following:
#define GPIO_PATH_BASE "/sys/class/gpio/gpio"
#define GPIO_PATH_DIRECTION "/direction"
#define GPIO_PATH_VALUE "/value"
int open_gpio(const char * port) {
char * base_path = (char *) malloc(sizeof(GPIO_PATH_BASE) + sizeof(port));
strcpy(base_path, GPIO_PATH_BASE);
strcat(base_path, port);
char * value_path = (char *) malloc(sizeof(base_path) + sizeof(GPIO_PATH_VALUE));
strcpy(value_path, (const char *) base_path);
strcat(value_path, GPIO_PATH_VALUE);
char * dir_path = (char *) malloc(sizeof(base_path) + sizeof(GPIO_PATH_DIRECTION));
strcpy(dir_path, (const char *) base_path);
strcat(dir_path, GPIO_PATH_DIRECTION);
}
I am actually quite unhappy with this approach. Is there a possibility to let a macro this stuff for me or should I create a helper function?
Bodo
You can make a function that takes two parts, allocates the space, and concatenates them. This should reduce the code duplication, while keeping your code readable:
static char *concat(const char* prefix, const char* suffix) {
size_t len = strlen(prefix) + strlen(suffix) + 1;
char *res = malloc(len);
strcpy(res, prefix);
strcat(res, suffix);
return res;
}
Now you can use this function as follows:
char * base_path = concat(GPIO_PATH_BASE, port);
char * value_path = concat(base_path, GPIO_PATH_VALUE);
char * dir_path = concat(base_path, GPIO_PATH_DIRECTION);
I find sprintf (or snprintf as mentionned by #larsmans) more suitable for string manipulations, especially if you want to add decimal values in your string.
I would use PATH_MAX (defined in limits.h) to have a statically allocated buffer like:
#include <limits.h>
#include <stdio.h>
unsigned char path[PATH_MAX];
#define GPIO_PATH_BASE "/sys/class/gpio/gpio"
#define GPIO_PATH_VALUE "/value"
int main(void)
{
snprintf(path, PATH_MAX, "%s/%d%s", GPIO_PATH_BASE, 42, GPIO_PATH_VALUE);
puts(path);
return 0;
}
$ make main
cc main.c -o main
$ ./main
/sys/class/gpio/gpio/42/value
$
If your system supports it, then asprintf() is the easiest mechanism:
#define GPIO_PATH_BASE "/sys/class/gpio/gpio"
#define GPIO_PATH_DIRECTION "/direction"
#define GPIO_PATH_VALUE "/value"
int open_gpio(const char * port)
{
char *base_path = asprintf("%s%s", GPIO_PATH_BASE, port);
char *value_path = asprintf("%s%s", base_path, GPIO_PATH_VALUE);
char *dir_path = asprintf("%s%s", base_path, GPIO_PATH_DIRECTION);
//...do some work with these...or return them...
//...should check for failed allocations, too...
}
If your system doesn't support asprintf(), you can 'fake' it with:
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
/* Should be in a header */
#ifndef HAVE_ASPRINTF
extern int asprintf(char **ret, const char *format, ...);
extern int vasprintf(char **ret, const char *format, va_list args);
#endif
#ifndef HAVE_ASPRINTF
int vasprintf(char **ret, const char *format, va_list args)
{
va_list copy;
va_copy(copy, args);
/* Make sure return pointer is determinate */
*ret = 0;
int count = vsnprintf(NULL, 0, format, args);
if (count >= 0)
{
char* buffer = malloc(count + 1);
if (buffer != NULL)
{
count = vsnprintf(buffer, count + 1, format, copy);
if (count < 0)
{
free(buffer);
buffer = 0;
}
*ret = buffer;
}
}
va_end(copy);
return count;
}
int asprintf(char **ret, const char *format, ...)
{
va_list args;
va_start(args, format);
int count = vasprintf(ret, format, args);
va_end(args);
return(count);
}
#endif /* HAVE_ASPRINTF */
I quite like to use sprintf to generate strings like this. But that assumes that you have a reasonable maximum size that you know won't be exceeded.
Of course, that's at least a little better than sizeof(base_path), which is completely wrong.
Using malloc also seems like a bad idea for variables that aren't being visible outside the module.
If we assume that port is the correct string, something like this:
char base_path[100];
sprintf(base_path, "%s/%s", GPIO_PATH_BASE, port);
I've discovered weird behavior of vsprintf on OSX.
This is my code:
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#if defined(WIN32)
#include <windows.h>
#define VSNPRINTF _vsnprintf
#elif defined(LINUX) || defined (DARWIN)
#define VSNPRINTF vsnprintf
#include <sys/types.h>
#include <unistd.h>
#endif
char *f(const char *fmt, ...)
{
char *out = NULL;
const int step = 32;
int n = -1, lout = step;
va_list arg;
if(fmt!=NULL)
{
va_start(arg, fmt);
do
{
if(!out)
{
free(out);
out = NULL;
}
out = (char*)malloc(lout + 1);
if(!out) break;
memset(out, 0, lout + 1);
n = VSNPRINTF(out, lout, fmt, arg);
if(n == -1 || n + 1 > lout)
{
lout += step;
n = -1;
}
}while(n == -1);
va_end(arg);
}
return out;
}
int main()
{
char *msg = NULL;
unsigned long x = 0xDEADBEEF;
msg = f("%X%X%X%X", x, x, x, x);
if(!msg) return -1;
puts(msg);
return 0;
}
The function shall return allocated string (char*) containing formatted text. It works correctly on Linux and Windows. It returns badly formatted text on OSX and sometimes it leads to Segmentation fault (EXC_BAD_ACCESS). Btw, I know that I can use vasprintf.
What can be the problem?
Your problem is most likely that you're calling vsnprintf with the same va_list multiple times. This doesn't work in some ABIs.
Look up the man page of va_copy. The short version is to do something like this:
va_list c;
va_copy(c, arg);
n = VSNPRINTF(out, lout, fmt, c);
va_end(c);
I have a program which does concatenation.
its like char *testConc(int a,..)
Where a indicates number of arguments are being passed for concatenation.
As legth keeps on changing is there is anything like constructor overloading in C
or any simple syntax which implements the functionality
Yes, there are varadic functions
#include <stdio.h>
#include <stdarg.h>
/* print all non-negative args one at a time;
all args are assumed to be of int type */
void printargs(int arg1, ...)
{
va_list ap;
int i;
va_start(ap, arg1);
for (i = arg1; i >= 0; i = va_arg(ap, int))
printf("%d ", i);
va_end(ap);
putchar('\n');
}
int main(void)
{
printargs(5, 2, 14, 84, 97, 15, 24, 48, -1);
printargs(84, 51, -1);
printargs(-1);
printargs(1, -1);
return 0;
}
C does not have function overloading capabilities. The syntax you have is called a variadic function, which can be used to perform what you asked.
The textConc function would look something like this:
char *textConc(int argc, ...)
{
va_list args;
char *str = NULL;
size_t len = 0;
va_start(args, argc);
while (argc--)
{
/* next string */
const char *temp = va_arg(args, const char *);
size_t size = strlen(temp);
/* make room and copy over */
str = realloc(str, len+size+1);
memcpy(str+len, temp, size+1);
/* new length */
len += size;
}
va_end(args);
return str;
}
int main(int argc, char **argv)
{
char *example = textConc(4, "Hello", "All", "good", "morning");
puts(example);
free(example);
return 0;
}
If you use GCC, we can fake overloading completely, using a little help of macros.
Rename textConc to textConcN and use the following macros:
#define ARGCOUNT(...) (sizeof((const char *[]){__VA_ARGS__})/sizeof(const char *))
#define textConc(...) textConcN(ARGCOUNT(__VA_ARGS__), __VA_ARGS__)
int main(int argc, char **argv)
{
/* notice, no more need for the number of arguments */
char *example = textConc("Hello", "All", "good", "morning");
puts(example);
free(example);
return 0;
}
Functions can't be overloaded in C.
You could rewrite your function as char *testConc(const char *s, ...), where you mark the end of the list with NULL:
testConc("foo", "bar", "baz", "quux", (char *)0);
This makes adding changing the number of actual arguments easier. If you have a C99 compiler, you can even write a wrapping macro that adds the NULL for you:
#define TESTCONC(...) testConc(__VA_ARGS__, (char *)0)
Hey, I've been working on this problem to read numbers from a text file and store them in an array but for some reason can't get it to work. Any help would be appreciated. the assignment is to implement the markov chain algorithm. I've made the reading part and assigning the array in the main fun() but i keep getting undeclared identifier as an error. Here is the code:
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include "eprintf.h"
enum {
NPREF = 2, /* number of prefix words */
NHASH = 4093, /* size of state hash table array */
MAXGEN = 10000 /* maximum words generated */
};
typedef struct State State;
typedef struct Suffix Suffix;
struct State { /* prefix + suffix list */
char *pref[NPREF]; /* prefix words */
Suffix *suf; /* list of suffixes */
State *next; /* next in hash table */
};
struct Suffix { /* list of suffixes */
char *word; /* suffix */
Suffix *next; /* next in list of suffixes */
};
State *lookup(char *prefix[], int create);
void build(char *prefix[], FILE*);
void generate(int nwords);
void add(char *prefix[], char *word);
State *statetab[NHASH]; /* hash table of states */
char NONWORD[] = "\n"; /* cannot appear as real word */
//FILE* random_reader;
//FILE* myfile;
/* markov main: markov-chain random text generation */
int main(void)
{
int i, nwords = MAXGEN;
char *prefix[NPREF]; /* current input prefix */
FILE* random_reader;
FILE* myfile;
int c;
//long seed;
setprogname("markov");
//seed = time(NULL);
//srand(seed);
random_reader = fopen("../random_num.txt","r");
myfile = fopen("../alice30.txt","r");
int element;
int random_num[10000];
char line; //each number
int i=0;
while(fgets(line, 20, random_reader)!=NULL) // update the array
{
sscanf(line,"%o",&element);
random_num[i]=element;
i++;
}
for (i = 0; i < NPREF; i++) /* set up initial prefix */
prefix[i] = NONWORD;
build(prefix, stdin);
add(prefix, NONWORD);
generate(nwords);
return 0;
}
const int MULTIPLIER = 31; /* for hash() */
/* hash: compute hash value for array of NPREF strings */
unsigned int hash(char *s[NPREF])
{
unsigned int h;
unsigned char *p;
int i;
h = 0;
for (i = 0; i < NPREF; i++)
for (p = (unsigned char *) s[i]; *p != '\0'; p++)
h = MULTIPLIER * h + *p;
return h % NHASH;
}
/* lookup: search for prefix; create if requested. */
/* returns pointer if present or created; NULL if not. */
/* creation doesn't strdup so strings mustn't change later. */
State* lookup(char *prefix[NPREF], int create)
{
int i, h;
State *sp;
h = hash(prefix);
for (sp = statetab[h]; sp != NULL; sp = sp->next) {
for (i = 0; i < NPREF; i++)
if (strcmp(prefix[i], sp->pref[i]) != 0)
break;
if (i == NPREF) /* found it */
return sp;
}
if (create) {
sp = (State *) emalloc(sizeof(State));
for (i = 0; i < NPREF; i++)
sp->pref[i] = prefix[i];
sp->suf = NULL;
sp->next = statetab[h];
statetab[h] = sp;
}
return sp;
}
/* addsuffix: add to state. suffix must not change later */
void addsuffix(State *sp, char *suffix)
{
Suffix *suf;
suf = (Suffix *) emalloc(sizeof(Suffix));
suf->word = suffix;
suf->next = sp->suf;
sp->suf = suf;
}
/* add: add word to suffix list, update prefix */
void add(char *prefix[NPREF], char *suffix)
{
State *sp;
sp = lookup(prefix, 1); /* create if not found */
addsuffix(sp, suffix);
/* move the words down the prefix */
memmove(prefix, prefix+1, (NPREF-1)*sizeof(prefix[0]));
prefix[NPREF-1] = suffix;
}
/* build: read input, build prefix table */
void build(char *prefix[NPREF], FILE *f)
{
char buf[100], fmt[10];
/* create a format string; %s could overflow buf */
sprintf(fmt, "%%%ds", sizeof(buf)-1);
while (fscanf(f, fmt, buf) != EOF)
add(prefix, estrdup(buf));
}
/* generate: produce output, one word per line */
void generate(int nwords)
{
State *sp;
Suffix *suf;
char *prefix[NPREF], *w;
int i, nmatch;
for (i = 0; i < NPREF; i++) /* reset initial prefix */
prefix[i] = NONWORD;
for (i = 0; i < nwords; i++) {
sp = lookup(prefix, 0);
if (sp == NULL)
eprintf("internal error: lookup failed");
nmatch = 0;
for (suf = sp->suf; suf != NULL; suf = suf->next)
if (rand() % ++nmatch == 0) /* prob = 1/nmatch */
w = suf->word;
if (nmatch == 0)
eprintf("internal error: no suffix %d %s", i, prefix[0]);
if (strcmp(w, NONWORD) == 0)
break;
printf("%s\n", w);
memmove(prefix, prefix+1, (NPREF-1)*sizeof(prefix[0]));
prefix[NPREF-1] = w;
}
}
******* Here are the eprintf header file**************
/* eprintf.h: error wrapper functions */
extern void eprintf(char *, ...);
extern void weprintf(char *, ...);
extern char *estrdup(char *);
extern void *emalloc(size_t);
extern void *erealloc(void *, size_t);
extern char *progname(void);
extern void setprogname(char *);
#define NELEMS(a) (sizeof(a) / sizeof(a[0]))
*******here is the eprintf source file*********
#include <stdio.h>
#include <stdlib.h>
#include "eprintf.h"
#include <stdarg.h>
#include <string.h>
#include <errno.h>
static char *name = NULL; /* program name for messages */
/* eprintf: print error message and exit */
void eprintf(char *fmt, ...)
{
va_list args;
fflush(stdout);
if (progname() != NULL)
fprintf(stderr, "%s: ", progname());
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
if (fmt[0] != '\0' && fmt[strlen(fmt)-1] == ':')
fprintf(stderr, " %s", strerror(errno));
fprintf(stderr, "\n");
exit(2); /* conventional value for failed execution */
}
/* weprintf: print warning message */
void weprintf(char *fmt, ...)
{
va_list args;
fflush(stdout);
fprintf(stderr, "warning: ");
if (progname() != NULL)
fprintf(stderr, "%s: ", progname());
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
if (fmt[0] != '\0' && fmt[strlen(fmt)-1] == ':')
fprintf(stderr, " %s\n", strerror(errno));
else
fprintf(stderr, "\n");
}
/* emalloc: malloc and report if error */
void *emalloc(size_t n)
{
void *p;
p = malloc(n);
if (p == NULL)
eprintf("malloc of %u bytes failed:", n);
return p;
}
/* erealloc: realloc and report if error */
void *erealloc(void *vp, size_t n)
{
void *p;
p = realloc(vp, n);
if (p == NULL)
eprintf("realloc of %u bytes failed:", n);
return p;
}
/* estrdup: duplicate a string, report if error */
char *estrdup(char *s)
{
char *t;
t = (char *) malloc(strlen(s)+1);
if (t == NULL)
eprintf("estrdup(\"%.20s\") failed:", s);
strcpy(t, s);
return t;
}
/* progname: return stored name of program */
char *progname(void)
{
return name;
}
/* setprogname: set stored name of program */
void setprogname(char *str)
{
name = estrdup(str);
}
It is very important that you read compiler error message from the top down. You got 3 C2143 errors before you got the C2065 error. It is typical that error messages get less accurate and informative, an earlier error may produce a slew of additional errors. The first message complains about the element variable declaration. Then you get additional errors for any line that contains element since the compiler couldn't properly parse the declaration.
Your compiler requires you to put all variable declarations before the code that uses them.
Also note that you've got two declarations for the i variable. And that line needs to be an array of char: char line[20]; Moving the file reading code into a separate function would be a rather good idea.
In main() you have variable definitions appearing after code. This is permissible in C99 but not in C89, so if you're using an old C89 compiler, or something like MSVC which still doesn't support C99, then this is not going to compile. Move this block:
int element;
int random_num[10000];
char line; //each number
int i=0;
up above the code before it so that your variable definitions precede any actual code.