I'm trying to reuse some old Flask web application from 2-3 years ago that seems to have broken in the interim.
I'm trying to figure out what the problem is but I'm having trouble debugging systematically.
Sorry I can't provide more specific code, the program is way too large and the problem is basically unknown. If I had to guess, the problem was happening in this segment:
elif resource=="shelfquery":
print ("Shelf")
if request.method=="PUT":
userInput=request.form['userInput']
print ("Shelf " + userInput)
cur.execute ("SELECT * FROM picDB")
for i in range (cur.rowcount):
value=cur.fetchone ()
if value is not None:
searchTerm=value [0]
print ("searchDB|")
print (searchTerm)
validInput=True
try:
# searchFind= ("SELECT searchString,pureJSON FROM nytDB where searchString LIKE %s")
# searchVal= user
if ("searchString" not in userInput and "searchDB" not in userInput and "DROP TABLE" not in userInput
and "DELETE " not in userInput and "pureJSON" not in userInput and "*" not in userInput):
cur.execute ("SELECT searchString,pureJSON FROM searchDB where searchString LIKE %s", [userInput])
else:
validInput=False
except (MySQLdb.Error) as e:
print ("Error1")
print (e)
print ("Row count ")
# print (cur.rowcount)
if cur.rowcount<=0:
searchUrl=shelffURL + userInput + shelffURL2
response = urllib2.urlopen(searchUrl)
content=response.read ()
jsonBalls= json.loads (content.decode ())
if ("searchString" not in userInput and "searchDB" not in userInput and "DROP TABLE" not in userInput
and "DELETE " not in userInput and "pureJSON" not in userInput and "*" not in userInput):
cur.execute ("INSERT IGNORE INTO searchDB (searchString,pureJSON,readStatus) VALUES (%s,%s,%s)" ,(userInput,content,"unread"))
db.commit ()
else:
print ("Invalid syntax, blocked to avoid SQL Injection")
validInput=False
return jsonify (jsonBalls)
elif cur.rowcount>0 and validInput==True:
value=cur.fetchone ()
searchStringValue=value [0]
jsonValue= value[1]
# print ("Getting from searchDB")
# print (searchStringValue)
jsonValue2=json.loads (jsonValue.decode ())
print (jsonValue)
return jsonify (jsonValue2)
else:
return None
Since that is often where the segfault happens (though not the only place) . Corresponding javascript/jquery code:
function addToBookShelf(methodType){
console.log ("Adding");
var userInputValue;
console.log (userInputValue);
if(methodType == "PUT" || methodType == "POST"){
userInputValue = $('#userInput').val();
}else {
userInputValue=methodType;
methodType="PUT";
}
/*
jQuery ajax does not send undefined data, so GET and DEL
are sent without any params when userInputValue is not
initialized.
*/
console.log ("Shelf query");
var picURL;
$.ajax({
method: methodType,
url: "/shelfquery",
data: { userInput: encodeURI(userInputValue) }
})
.done(function( msg ) {
console.log (msg);
console.log ("Time to get photos");
//$('#gallery').empty ();
// for (i = 0; i<10 ; i++) {
$.ajax({
method: methodType,
url: "/picquery",
data: { userInput: encodeURI(userInputValue) }
})
.done(function( msg2 ) {
console.log ("Save");
console.log (msg2);
id=msg2.items[0].volumeInfo.industryIdentifiers[0].identifier;
volumeID=msg2.items[0].id;
desc=msg2.items[0].volumeInfo.description;
picURL=JSON.stringify(msg2['items'][0]['volumeInfo']['imageLinks']['thumbnail']);
divStart="<div class=\"panel panel-primary col-lg-3 col-md-4 col-xs-6 thumb\" id=\"" + id +".." + volumeID +"\">"
divMiddle="<div class=\"panel-body\">"
divImge= "<img src=" + picURL + "class=\"img-responsive center-block\" />"
divMiddleEnd="<div class=\"panel-image\">" +divImge + "<label for=\"toggle-4\"></label></div>"
category=JSON.stringify(msg2['items'][0]['volumeInfo']['industryIdentifiers']['categories']);
title=msg2.items[0].volumeInfo.title;
author =msg2.items[0].volumeInfo.authors[0];
categoryLine= "<p>" + category +"</p>"
previewLink=JSON.stringify(msg2['items'][0]['volumeInfo']['previewLink']);
previewLinkLine="<p><a href="+ previewLink +"> Preview Link</a></p>"
heading= "<div class=\"panel-heading\"><h3 class=\"panel-title\">" + title + " by " + author + "</h3></div>"
buttonFormat="<button class=\"next btn btn-success\">View More Info</button>"
buttonFormat2="<button class=\"endd btn btn-danger\">Delete from DB</button>"
midButtonFormat="<div class=\"btn-group\"><a class=\"reads btn btn-xs btn-success\" href=\"#\">Read</a><a class=\"readngs btn btn-xs btn-warning\" href=\"#\">Reading</a><a class=\"unreads btn btn-xs btn-danger\" href=\"#\">Unread</a></div></div>"
reviewCount=JSON.stringify (msg['books'][0]['average_rating']);
goodReadsRating= "<p> Average GoodReads Rating: " +reviewCount +"</p>"
finalLine=divStart+ heading + divMiddle +divMiddleEnd + "<div class=\"panel-body\" id=\"" + id + ".." + volumeID + ".." + title + ".." + author + ".." + desc + "\">" + goodReadsRating + previewLinkLine + buttonFormat +buttonFormat2+midButtonFormat;
$('#gallery').append (finalLine);
})
.fail(function() {
console.log ("Failed, totally");
});
})
.fail(function() {
console.log ("Failed before photos");
});
Basically, the structure is that I have a python file for the flask and javascript for the scripts running in the static webpages (and a MySQL database -using MySQLDB, from a few years ago).
However, I keep getting segfaults and "double free or corruption (!prev)" errors and, rarely, errors like "GC object already tracked".
I can't seem to figure out which side the error is coming from because it seems to be one of those floating errors (or the problem is simply systemic). I cut this out, the program segfaults on a different area.
I was wondering if anyone else had a way of debugging these sorts of programs? I tried GDB and it wasn't particularly useful.
Generally speaking, can I assume that a segfault would be coming from the javascript side? Would that be a place to start?
I do get some database hangs but I've changed databases a few times (from AWS to Google to local) just to check and I still keep getting segfaults when the errors seem to have been cut down on.
