I'm out of ideas...

**awsdert** · 01-28-2020

I've been trying to diagnose why my app stopped finding itself in /proc and now I've run out of ideas on what the cause is (cause I fixed every problem I found besides this one) so now I'm asking peops to have a look at the last code executed before the loop dies on the 1st attempt.

Code:

	while ( (ent = readdir(glance->dir)) ) {
		if ( ent->d_name[0] < '0' || ent->d_name[0] > '9' )
			continue;
		(void)sscanf( ent->d_name, "%d", &entryId );
		notice->ownerId = entryId;
		while ( proc_notice_info( err, notice->ownerId, notice ) )
		{
			if ( notice->ownerId == glance->underId )
				return proc_notice_info( err, entryId, notice );
			if ( notice->ownerId <= 0 )
				break;
		}
	}
	if ( err ) *err = EXIT_SUCCESS;
	proc_glance_shut( glance );
	return NULL;
...
proc_notice_t* proc_notice_info(
	int *err, int pid, proc_notice_t *notice )
{
	int fd;
	char path[256] = {0};
	space_t *full, *key, *val, *name;
	kvpair_t *kvpair;
	int ret;
	char *txt, *k, *v;
	intptr_t size;
	if ( !notice ) {
		if ( err ) *err = EDESTADDRREQ;
		ERRMSG( EDESTADDRREQ, "notice was NULL" );
		return NULL;
	}
	kvpair = &(notice->kvpair);
	name = &(notice->name);
	full = &(kvpair->full);
	key = &(kvpair->key);
	val = &(kvpair->val);
	memset( name->block, 0, name->given );
	memset( full->block, 0, full->given );
	memset( key->block, 0, key->given );
	memset( val->block, 0, val->given );
	notice->ownerId = -1;
	notice->entryId = pid;
	sprintf( path, "/proc/%d/status", pid );
	/* Implements a fallback looped read call in the event lseek gleans
	 * nothing */
	if ( !(size = file_get_size( &ret, path )) ) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't get status size" );
		return NULL;
	}
	if ( (fd = open(path,O_RDONLY)) < 0 ) {
		if ( err ) *err = errno;
		ERRMSG( errno, "Couldn't open status file" );
		printf( "File '%s'\n", path );
		return NULL;
	}
	if ( !more_space( &ret, full, size )) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't allocate memory to read into" );
		fprintf( stderr, "Wanted %zu bytes\n", size );
		close(fd);
		return NULL;
	}
	if ( !gasp_read(fd, full->block, full->given) ) {
		close(fd);
		ret = ENODATA;
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't read the status file" );
		return NULL;
	}
	/* No longer need the file opened since we have everything */
	close(fd);
	if ( (ret = change_kvpair(
		kvpair, full->given,
		full->given, full->given, 1 )) != EXIT_SUCCESS ) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't allocate memory for key/val pair" );
		return NULL;
	}
	/* Ensure we have enough space for the name */
	if ( !more_space( &ret, name, full->given ) ) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't allocate memory for name");
		return NULL;
	}
	txt = strstr( full->block, "\n" );
	if ( !txt ) {
		ret = ENOSYS;
		if ( err ) *err = ret;
		ERRMSG( ret, "Don't know how to handle the status file" );
		return NULL;
	}
	/* Don't want strlen to count through everything */
	*txt = 0;
	/* Find the start of the name given */
	v = strstr( (k = full->block), "\t" );
	if ( !v ) {
		ret = ENODATA;
		if ( *err ) *err = ret;
		ERRMSG( ret, "Couldn't find character '\t' in read text");
		(void)fprintf(stderr,"read '%s'\n", full->block );
		return NULL;
	}
	++v;
	/* Fill name with the name given */
	memcpy( name->block, v, strlen(v) );
	/* Restore ability for strstr to see next character */
	*txt = '\n';
	while ( (k = txt = strstr( txt, "\n" )) ) {
		*k = 0; ++k;
		v = strstr( k, "\t" );
		*v = 0;
		/* This is currently the only value we care about besides the
		 * name */
		if ( strcmp( k, "PPid:" ) == 0 ) break;
		*v = '\t';
		*(--k) = '\n';
		++txt;
	}
	if ( !txt ) {
		ret = ENOENT;
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't locate ownerId" );
		return NULL;
	}
	/* Just in case we decide to take more parameters */
	*v = '\t';
	sscanf( txt, "%d",	&(notice->ownerId) );
	if ( err ) *err = EXIT_SUCCESS;
	return notice;
}

**Salem** · 01-28-2020

> while ( (ent = readdir(glance->dir)) )
So which dir are you reading here?

My guess is /proc is changed for some reason (maybe a process got added or removed), and that invalidated your directory iterator before you got to the end.

Maybe read all the pids in one loop, quickly, with no I/O.
Then use another loop to read all those pids, or at least verify that itself is in the list.

I generally find most of your code to be unreadable, possibly because it comes across as a wall of text.
A few blank lines between each block of code wouldn't go amiss.

**awsdert** · 01-28-2020

Originally Posted by Salem

> while ( (ent = readdir(glance->dir)) )
So which dir are you reading here?

My guess is /proc is changed for some reason (maybe a process got added or removed), and that invalidated your directory iterator before you got to the end.

Maybe read all the pids in one loop, quickly, with no I/O.
Then use another loop to read all those pids, or at least verify that itself is in the list.

I generally find most of your code to be unreadable, possibly because it comes across as a wall of text.
A few blank lines between each block of code wouldn't go amiss.

Ah that's what peops were refering to when they say unreadable, I'll try to fix that then, as for the invalidated bit I guess that makes sense I'll switch to an ID list then, still fits with the glance concept after all

**awsdert** · 01-28-2020

Still running into the same issue, somehow every ID I iterate through is 0, I'll post the change here plus the function that fills the list, tried making it more "readable" though if I'm honest I liked it better before where I didn't have to scroll as much.

Code:

for ( ; glance->process < glance->idNodes.count; glance->process++ )
	{
		notice->ownerId = *(
			((int*)(glance->idNodes.space.block)) + glance->process);

		while ( proc_notice_info( err, notice->ownerId, notice ) )
		{
			if ( notice->ownerId == glance->underId )
				return proc_notice_info( err, entryId, notice );
			if ( notice->ownerId <= 0 )
				break;
		}
	}

	if ( err ) *err = EXIT_SUCCESS;
	proc_glance_shut( glance );
	return NULL;
}

proc_notice_t*
	proc_glance_open( int *err, proc_glance_t *glance, int underId ) {
	int ret = errno = EXIT_SUCCESS;
	DIR *dir;
	struct dirent *ent;
	node_t i = 0;
	if ( !glance ) {
		if ( err ) *err = EDESTADDRREQ;
		ERRMSG( EDESTADDRREQ, "glance was NULL" );
		return NULL;
	}
	(void)memset( glance, 0, sizeof(proc_glance_t) );
	glance->underId = underId;
	if ( more_nodes( int, &ret, &(glance->idNodes), 2000 ) ) {
		if ( (dir = opendir("/proc")) ) {
			
			while ( (ent = readdir( dir )) ) {
				if ( ent->d_name[0] < '0' && ent->d_name[0] > '9' )
					continue;

				if ( (ret = add_node(
					&(glance->idNodes), &i, sizeof(int) ))
					!= EXIT_SUCCESS )
					break;

				sscanf( ent->d_name, "%d",
					((int*)(glance->idNodes.space.block)) + i );
			}
			closedir(dir);
			
			if ( glance->idNodes.count )
				return proc_notice_next( err, glance );
		}
	}
	ret = ( errno != EXIT_SUCCESS ) ? errno : EXIT_FAILURE;
	if ( err ) *err = ret;
	ERRMSG( ret, "glance->dir was NULL" );
	return NULL;
}
...
proc_notice_t* proc_notice_info(
	int *err, int pid, proc_notice_t *notice )
{
	int fd;
	char path[256] = {0};
	space_t *full, *key, *val, *name;
	kvpair_t *kvpair;
	int ret;
	char *txt, *k, *v;
	intptr_t size;
	
	if ( !notice ) {
		if ( err ) *err = EDESTADDRREQ;
		ERRMSG( EDESTADDRREQ, "notice was NULL" );
		return NULL;
	}
	
	kvpair = &(notice->kvpair);
	name = &(notice->name);
	full = &(kvpair->full);
	key = &(kvpair->key);
	val = &(kvpair->val);
	
	memset( name->block, 0, name->given );
	memset( full->block, 0, full->given );
	memset( key->block, 0, key->given );
	memset( val->block, 0, val->given );
	
	notice->ownerId = -1;
	notice->entryId = pid;
	sprintf( path, "/proc/%d/status", pid );
	
	/* Implements a fallback looped read call in the event lseek gleans
	 * nothing */
	if ( !(size = file_get_size( &ret, path )) ) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't get status size" );
		return NULL;
	}
	
	if ( (fd = open(path,O_RDONLY)) < 0 ) {
		if ( err ) *err = errno;
		ERRMSG( errno, "Couldn't open status file" );
		printf( "File '%s'\n", path );
		return NULL;
	}
	
	if ( !more_space( &ret, full, size )) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't allocate memory to read into" );
		fprintf( stderr, "Wanted %zu bytes\n", size );
		close(fd);
		return NULL;
	}
	
	if ( !gasp_read(fd, full->block, full->given) ) {
		close(fd);
		ret = ENODATA;
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't read the status file" );
		return NULL;
	}
	
	/* No longer need the file opened since we have everything */
	close(fd);
	if ( (ret = change_kvpair(
		kvpair, full->given,
		full->given, full->given, 1 )) != EXIT_SUCCESS ) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't allocate memory for key/val pair" );
		return NULL;
	}
	
	/* Ensure we have enough space for the name */
	if ( !more_space( &ret, name, full->given ) ) {
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't allocate memory for name");
		return NULL;
	}
	
	txt = strstr( full->block, "\n" );
	if ( !txt ) {
		ret = ENOSYS;
		if ( err ) *err = ret;
		ERRMSG( ret, "Don't know how to handle the status file" );
		return NULL;
	}
	
	/* Don't want strlen to count through everything */
	*txt = 0;
	
	/* Find the start of the name given */
	v = strstr( (k = full->block), "\t" );
	if ( !v ) {
		ret = ENODATA;
		if ( *err ) *err = ret;
		ERRMSG( ret, "Couldn't find character '\t' in read text");
		(void)fprintf(stderr,"read '%s'\n", full->block );
		return NULL;
	}
	
	/* We don't want to copy the tab character */
	++v;
	
	/* Fill name with the name given */
	memcpy( name->block, v, strlen(v) );
	
	/* Restore ability for strstr to see next character */
	*txt = '\n';
	
	while ( (k = txt = strstr( txt, "\n" )) ) {
		*k = 0; ++k;
		v = strstr( k, "\t" );
		*v = 0;
		/* This is currently the only value we care about besides the
		 * name */
		if ( strcmp( k, "PPid:" ) == 0 ) break;
		*v = '\t';
		*(--k) = '\n';
		++txt;
	}
	
	if ( !txt ) {
		ret = ENOENT;
		if ( err ) *err = ret;
		ERRMSG( ret, "Couldn't locate ownerId" );
		return NULL;
	}
	
	/* Just in case we decide to take more parameters */
	*v = '\t';
	sscanf( txt, "%d",	&(notice->ownerId) );
	if ( err ) *err = EXIT_SUCCESS;
	return notice;
}

**awsdert** · 01-28-2020

Whoops just realised I forgot to change the && to on this line:

Code:

if ( ent->d_name[0] < '0' && ent->d_name[0] > '9' )
	continue;

Didn't resolve my problem of not finding itself but did resolve the list of 0s I saw

**Structure** · 01-28-2020

while (ent = readdir(glance->dir))

does this loop ever exit ?

if ( !(size = file_get_size( &ret, path )) )

if (dir = opendir("/proc"))

take a look at this: Operators in C

**laserlight** · 01-28-2020

Originally Posted by Structure

does this loop ever exit ?

Yes, because at some point readdir will return a null pointer.

**Structure** · 01-28-2020

Code:

while (ent = readdir(glance->dir)) {}

does this loop ever exit ?

Yes, because at some point readdir will return a null pointer.

**laserlight** · 01-28-2020

Originally Posted by Structure

take a look at this: Operators in C

You might want to say what's wrong with awsdert's code such that taking a look at that webpage makes sense. I note that awsdert's code does suppress a common compiler warning associated with using such assignments within conditionals, i.e., by wrapping it in an extra pair of parentheses to signal that the assignment was deliberate rather than a typo for == whereas your paraphrase of awsdert's code omits those parentheses.

**Structure** · 01-28-2020

wrapping it in an extra pair of parentheses to signal that the assignment was deliberate rather than a typo

are you saying the compiler switches out the = with == ?

You might want to say what's wrong with awsdert's code

to see if 2 values are equal you would:

Code:

if ( a == b ) { };

if a is equal to b it will run the block.

Code:

if ( a = b ) { };

at this point you set a to b and you are no longer comparing.
i believe it will always be true and run the block.

i.e:

Code:

if ( !(size = file_get_size( &ret, path )) ){ };

should never run the block since size will always be equal to the value you set it to.

**laserlight** · 01-28-2020

readdir is not part of standard C, but it is POSIX standard, so if you don't know how readdir works, it's pretty easy to find out because POSIX stuff tends to be online via web-based manual pages and such.

Originally Posted by Structure

are you saying the compiler switches out the = with == ?

No. The assignment is intentional. Comparing for equality would be a bug because those variables have not been set to an initial value at that point.

**Structure** · 01-28-2020

The assignment is intentional

Some things you guys do i can understand. Others i can't and most likely never will.
What i can tell you is it obviously doesn't work the way it's being done.

if ( !(size = file_get_size( &ret, path )) ) { };

I would be shocked that block of code ever gets executed.

**awsdert** · 01-28-2020

Oh wow, I watch a vid or 2 and come back to find my thread far busier than expected XD
Glad to see at least 1 person understood the assignment was intentional though

Still I wish I could figure out why my app can't find itself 😓

**awsdert** · 01-28-2020

Originally Posted by Structure

Some things you guys do i can understand. Others i can't and most likely never will.
What i can tell you is it obviously doesn't work the way it's being done.

I would be shocked that block of code ever gets executed.

Prepare to be shocked then... cause it does

**Structure** · 01-28-2020

at some point readdir will return a null pointer.

Code:

#include <stdio.h>

int main() {
    int a = 100, *b;
    if ( !(a = *b) ) {
        printf("interesting.");
    };
};

Code:

if ( !(a = b) ) {  
  printf("fails.");
};

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