Fix #14798: internalError on sscanf format string (#8724)

Author: ludviggunne

lib/checkio.cpp

@@ -841,6 +841,8 @@ void CheckIOImpl::checkFormatString(const Token * const tok,
                 }
                 ++i;
             }
+            while (!width.empty() && width[0] == '0')
+                width = width.substr(1);
             auto bracketBeg = formatString.cend();
             if (i != formatString.cend() && *i == '[') {
                 bracketBeg = i;

test/testio.cpp

@@ -53,6 +53,7 @@ class TestIO : public TestFixture {
         TEST_CASE(testScanf3); // #3494
         TEST_CASE(testScanf4); // #ticket 2553
         TEST_CASE(testScanf5); // #10632
+        TEST_CASE(testScanf6);
 
         mNewTemplate = false;
         TEST_CASE(testScanfArgument);
@@ -892,6 +893,14 @@ class TestIO : public TestFixture {
                       "[test.cpp:3:5]: (error) Width 42 given in format string (no. 2) is larger than destination buffer 's2[42]', use %41[a-z] to prevent overflowing it. [invalidScanfFormatWidth]\n", errout_str());
     }
 
+    void testScanf6() {
+        ASSERT_NO_THROW(check("int f(const char *p) {\n"
+                              "        char a[3];\n"
+                              "        return sscanf(p, \"%02s\", a);\n"
+                              "}\n"));
+        ASSERT_EQUALS("", errout_str());
+    }
+
 
 #define TEST_SCANF_CODE(format, type) \
     "void f(){" type " x; scanf(\"" format "\", &x);}"