fix: error when an interactive param is also connected (#2121)

When a parameter is interactive and connected, the connection should
win. OSL was incorrectly treating the interactive trait as taking
precedence, attempting to write into the read-only interactive buffer
during shader execution.

Fixed both single point and batch modes.

---------

Signed-off-by: Chris Hellmuth <chellmuth@gmail.com>

Author: chellmuth

src/cmake/testing.cmake

@@ -356,7 +356,7 @@ macro (osl_add_all_tests)
                 printf-reg
                 printf-whole-array
                 raytype raytype-reg raytype-specialized regex-reg
-                reparam reparam-arrays reparam-string testoptix-reparam
+                reparam reparam-arrays reparam-connected-crash reparam-string testoptix-reparam
                 render-background render-bumptest
                 render-bunny
                 render-cornell

src/liboslexec/backendllvm.cpp

@@ -232,7 +232,8 @@ BackendLLVM::getLLVMSymbolBase(const Symbol& sym)
                                 llvm_type(sym.typespec().elementtype()));
         return result;
     }
-    if (sym.symtype() == SymTypeParam && sym.interactive()) {
+    if (sym.symtype() == SymTypeParam && sym.interactive()
+        && !sym.connected()) {
         // Special case for interactively-edited parameters -- they live in
         // the interactive data block for the group.
         // Generate the pointer to this symbol by offsetting into the

src/liboslexec/batched_backendllvm.cpp

@@ -454,7 +454,8 @@ BatchedBackendLLVM::getLLVMSymbolBase(const Symbol& sym)
         return result;
     }
 
-    if (sym.symtype() == SymTypeParam && sym.interactive()) {
+    if (sym.symtype() == SymTypeParam && sym.interactive()
+        && !sym.connected()) {
         // Special case for interactively-edited parameters -- they live in
         // the interactive data block for the group.
         // Generate the pointer to this symbol by offsetting into the

testsuite/reparam-connected-crash/BATCHED

@@ -0,0 +1,11 @@
+// Copyright Contributors to the Open Shading Language project.
+// SPDX-License-Identifier: BSD-3-Clause
+// https://github.com/AcademySoftwareFoundation/OpenShadingLanguage
+
+// Downstream layer: 'in' will be marked interactive with an instance value
+// via testshade -param:interactive=1
+shader downstream(float in = 0, output float result = 0)
+{
+    printf("in = %g\n", in);
+    result = in;
+}

testsuite/reparam-connected-crash/downstream.osl

@@ -0,0 +1,5 @@
+Compiled downstream.osl -> downstream.oso
+Compiled upstream.osl -> upstream.oso
+Connect upstream_layer.out to downstream_layer.in
+in = 0.5
+

testsuite/reparam-connected-crash/ref/out.txt

@@ -0,0 +1,23 @@
+#!/usr/bin/env python
+
+# Copyright Contributors to the Open Shading Language project.
+# SPDX-License-Identifier: BSD-3-Clause
+# https://github.com/AcademySoftwareFoundation/OpenShadingLanguage
+
+# Regression test: downstream input param is both connected (from upstream) and
+# marked interactive with an instance value.
+#
+# Bug: OSL give precedence to the interactive trait instead of connected. This
+# leads to an attempted write of the interactive buffer. However, the offset
+# is calculated incorrectly and the write occurs at interactive_buffer[-1].
+#
+# Correct output: in = 0.5 (u at the default shade point, from the connection)
+# Buggy output:   in = <garbage> (corrupted memory) or crash
+
+command += testshade(
+    "-layer upstream_layer upstream "
+    "-layer downstream_layer -param:interactive=1 in 9.0 downstream "
+    "-connect upstream_layer out downstream_layer in "
+)
+
+outputs = ["out.txt"]

testsuite/reparam-connected-crash/run.py

@@ -0,0 +1,8 @@
+// Copyright Contributors to the Open Shading Language project.
+// SPDX-License-Identifier: BSD-3-Clause
+// https://github.com/AcademySoftwareFoundation/OpenShadingLanguage
+
+shader upstream(output float out = 0)
+{
+    out = u; // don't constant-fold
+}