Fix another FP

Author: Your Name

lib/forwardanalyzer.cpp

@@ -424,7 +424,12 @@ namespace {
 
             if (terminate == Analyzer::Terminate::Escape) {
                 branch.escape = true;
-                branch.escapeUnknown = false;
+                // The traversal followed an escaping path, but if the scope does not structurally
+                // always escape then another path (e.g. a modified fork) falls through, so the escape
+                // is only conditional - keep isModified() meaningful by not treating it as conclusive.
+                bool structuralUnknown = false;
+                const bool structuralEscape = isEscapeScope(branch.endBlock, structuralUnknown);
+                branch.escapeUnknown = !structuralEscape || structuralUnknown;
             } else {
                 // Detect an escape the traversal did not flag (e.g. an unknown noreturn call);
                 // escapeUnknown reports a possible (unknown) escape.
@@ -557,7 +562,7 @@ namespace {
                         forkContinue = false;
                 }
 
-                if (allAnalysis.isModified() || !forkContinue) {
+                if (!forkContinue) {
                     // TODO: Don't bail on missing condition
                     if (!condTok)
                         return Break(Analyzer::Terminate::Bail);

test/testcondition.cpp

@@ -4922,6 +4922,19 @@ class TestCondition : public TestFixture {
               "    if (bits > 0) {}\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("int g();\n" // the modifying branch has an escaping sibling - still must be lowered
+              "void f(int t, int u) {\n"
+              "    int v = 0;\n"
+              "    if (t) {\n"
+              "        if (u == 2)\n"
+              "            v = g();\n"
+              "        else\n"
+              "            return;\n"
+              "    }\n"
+              "    if (v > 0) {}\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void alwaysTrueSymbolic()