fixup! fixup! fixup! fixup! fixup! fixup! fixup! Fix #958: warn when feof() is used as a while loop condition

Author: francois-berder

lib/checkio.cpp

@@ -481,7 +481,7 @@ void CheckIO::invalidScanfError(const Token *tok)
                 CWE119, Certainty::normal);
 }
 
-static bool findFileReadCall(const Token *start, const Token *end, int varid)
+static const Token* findFileReadCall(const Token *start, const Token *end, int varid)
 {
     const Token* found = Token::findmatch(start, "fgets|fgetc|getc|fread|fscanf (", end);
     while (found) {
@@ -491,11 +491,11 @@ static bool findFileReadCall(const Token *start, const Token *end, int varid)
                                ? args.front()->varId() == varid
                                : args.back()->varId() == varid;
             if (match)
-                return true;
+                return found;
         }
         found = Token::findmatch(found->next(), "fgets|fgetc|getc|fread|fscanf (", end);
     }
-    return false;
+    return nullptr;
 }
 
 void CheckIO::checkWrongfeofUsage()
@@ -509,15 +509,23 @@ void CheckIO::checkWrongfeofUsage()
             if (!Token::simpleMatch(tok, "while ( ! feof ("))
                 continue;
 
-            // Usage of feof is correct if a read happens before and within the loop
-            const Token *endCond = tok->linkAt(1);
-            const Token *endBody = endCond->linkAt(1);
-            const int fpVarId = tok->tokAt(5)->varId();
-
             // Bail out if we cannot identify file pointer
+            const int fpVarId = tok->tokAt(5)->varId();
             if (fpVarId == 0)
                 continue;
-            if (findFileReadCall(scope->bodyStart, tok, fpVarId) && findFileReadCall(tok, endBody, fpVarId))
+
+            // Usage of feof is correct if a read happens before and within the loop.
+            // However, if we find a control flow statement in between the fileReadCall
+            // token and the while loop condition, then we bail out.
+            const Token *endCond = tok->linkAt(1);
+            const Token *endBody = endCond->linkAt(1);
+
+            const Token *prevFileReadCallTok = findFileReadCall(scope->bodyStart, tok, fpVarId);
+            const Token *loopFileReadCallTok = findFileReadCall(tok, endBody, fpVarId);
+            const Token *prevControlFlowTok = Token::findmatch(prevFileReadCallTok, "return|break|goto|continue|throw", tok);
+            const Token *loopControlFlowTok = Token::findmatch(tok, "return|break|goto|continue|throw", loopFileReadCallTok);
+
+            if (prevFileReadCallTok && loopFileReadCallTok && !prevControlFlowTok && !loopControlFlowTok)
                 continue;
 
             wrongfeofUsage(getCondTok(tok));