Possible bug??? in dbReadDatabaseFP

["Dudley, David via Tech-talk" <tech-talk at aps.anl.gov>]

I wrote this little routine to allow me to load database records into the IOC upon startup.

 

 

// Set this to use 'tmpfile' to create a temprary file, or don't set to use tempname and create an actual file in /tmp

//#define USE_TMPFILE

void loadMyDatabaseRecords(void)

{

                char *pptr = NULL;

                char *subsPtr = NULL;

                FILE *tempFile = NULL;

                const char substring[] = "P=";

 

#ifndef USE_TMPFILE

                char nameTemplate[] = "BNET";

                char *tempName;

#endif

               

                /* Generate a temporary file, and write the database definition of the diagnostics record into it. */

#ifdef USE_TMPFILE

                tempFile = tmpfile();

#else

                tempName = tempnam(NULL, nameTemplate);

                printf("Opening %s\n",tempName);

                tempFile=fopen(tempName, "w+");

#endif

                if(tempFile) {

                                size_t i;

 

                                i=fputs(recordsDef, tempFile);

#ifdef USE_TMPFILE

                                // rewind the file to the start

                                rewind(tempFile);

#else

                                // If I'm using a file to do this, lets just close the file at the moment.

                                fclose(tempFile);

#endif

                                // Not quite ready yet, I need to fill out my "substitutions" buffer

                                pptr=getenv("IOCNAME");

                                i=strlen(substring)+strlen(pptr);

                                subsPtr = (char *) calloc(sizeof(char), i+1);

                                strncpy(subsPtr, substring, strlen(substring) );

                                strncat(subsPtr, pptr, strlen(pptr)+1);

                               

#ifdef USE_TMPFILE

                                printf("Loading new database\n");

                                // use dbReadDatabaseFP to load the file

                                dbReadDatabaseFP(&pdbbase, tempFile, NULL, subsPtr);

#else

                                printf("Loading my temp file %s\n",tempName);

                                // use dbReadDatabase to load the file

                                dbReadDatabase(&pdbbase, tempName, NULL, subsPtr);

                                free(tempName);

#endif

                                printf("Done\n");

                                free(subsPtr);

                                printf("Closing file\n");

#ifdef USE_TMPFILE

                                // Closing the file will delete it as well.

                                fclose(tempFile);

#else

#endif

                }

}

 

 

This is triggered during the iocInit startup during the initHookAtIocBuild state, and I’ve also tried it at the initHookAtBeginning state as well.

 

So, if I have ‘USE_TMPFILE’ defined, the routine uses ‘tmpfile’ and creates a temporary file, writes the database info to it, and then calls ‘dbReadDatabaseFP’.  If it’s not defined, the routine generates a temporary file, writes the database info into it, closes the file and uses ‘dbReadDatabase’ to load it.  There’s more maintenance needed in doing things with ‘dbReadDatabase’, but what the heck-

 

Now, here’s the rub…..

If I don’t define ‘USE_TMPFILE’, the routine generates a proper temporary file, writes a proper record to it, closes the file, etc… and calls ‘dbReadDatabase’ and works great.

 

If I do define ‘USE_TMPFILE’ (which was my original idea), it creates the temporary file, writes a proper record to it (I have checked this), and then calls ‘dbReadDatabaseFP’.

In this case, the IOC shows that it loaded the database, closed the file, and then I get a ‘free(): double free detected in tcache 2’ error and the IOC aborts.

 

This is with the latest version of EPICS 7 (just ‘git pull’d this morning, on Debian Bulldog.

 

Note that I’ve figured a way around this error, but want to report it just the same, in case this is a possible bug.

 

Later-

 

David Dudley Controls Engineer III Facility for Rare Isotope Beams Michigan State University 640 South Shaw Lane East Lansing, MI 48824-1321, USA Tel. 517-908-7133 Email: dudleyd@frib.msu.edu

 

 

// Set this to use 'tmpfile' to create a temprary file, or don't set to use tempname and create an actual file in /tmp
//#define USE_TMPFILE
void loadMyDatabaseRecords(void)
{
	char *pptr = NULL;
	char *subsPtr = NULL;
	FILE *tempFile = NULL;
	const char substring[] = "P=";

#ifndef USE_TMPFILE
	char nameTemplate[] = "BNET";
	char *tempName;
#endif
	
	/* Generate a temporary file, and write the database definition of the diagnostics record into it. */
#ifdef USE_TMPFILE
	tempFile = tmpfile();
#else
	tempName = tempnam(NULL, nameTemplate);
	printf("Opening %s\n",tempName);
	tempFile=fopen(tempName, "w+");
#endif
	if(tempFile) {
		size_t i;

		i=fputs(recordsDef, tempFile);
#ifdef USE_TMPFILE
		// rewind the file to the start
		rewind(tempFile);
#else
		// If I'm using a file to do this, lets just close the file at the moment.
		fclose(tempFile);
#endif
		// Not quite ready yet, I need to fill out my "substitutions" buffer
		pptr=getenv("IOCNAME");
		i=strlen(substring)+strlen(pptr);
		subsPtr = (char *) calloc(sizeof(char), i+1);
		strncpy(subsPtr, substring, strlen(substring) );
		strncat(subsPtr, pptr, strlen(pptr)+1);
		
#ifdef USE_TMPFILE
		printf("Loading new database\n");
		// use dbReadDatabaseFP to load the file
		dbReadDatabaseFP(&pdbbase, tempFile, NULL, subsPtr);
#else
		printf("Loading my temp file %s\n",tempName);
		// use dbReadDatabase to load the file
		dbReadDatabase(&pdbbase, tempName, NULL, subsPtr);
		free(tempName);
#endif
		printf("Done\n");
		free(subsPtr);
		printf("Closing file\n");
#ifdef USE_TMPFILE
		// Closing the file will delete it as well.
		fclose(tempFile);
#else
#endif
	}
}