From dfcd262aa5ca535e8542df897829ecb79dd4d412 Mon Sep 17 00:00:00 2001
From: Michael Chirico <chiricom@google.com>
Date: Thu, 23 Jul 2026 12:54:30 -0700
Subject: [PATCH 1/2] Always initialize c_options=NULL

---
 src/rinterface.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/rinterface.c b/src/rinterface.c
index d6c93c93b63..1ff2711494b 100644
--- a/src/rinterface.c
+++ b/src/rinterface.c
@@ -5323,7 +5323,7 @@ SEXP R_igraph_pagerank(SEXP graph, SEXP algo, SEXP vids, SEXP directed, SEXP dam
   igraph_real_t c_damping;
   igraph_vector_t c_weights;
   igraph_arpack_options_t c_options1;
-  void* c_options;
+  void* c_options = NULL;
   SEXP vector;
   SEXP value;
 
@@ -5396,7 +5396,7 @@ SEXP R_igraph_personalized_pagerank(SEXP graph, SEXP algo, SEXP vids, SEXP direc
   igraph_vector_t c_personalized;
   igraph_vector_t c_weights;
   igraph_arpack_options_t c_options1;
-  void* c_options;
+  void* c_options = NULL;
   SEXP vector;
   SEXP value;
 
@@ -5472,7 +5472,7 @@ SEXP R_igraph_personalized_pagerank_vs(SEXP graph, SEXP algo, SEXP vids, SEXP di
   igraph_vs_t c_reset_vids;
   igraph_vector_t c_weights;
   igraph_arpack_options_t c_options1;
-  void* c_options;
+  void* c_options = NULL;
   SEXP vector;
   SEXP value;
 

From a5a4a53c40dd049bd543a429f6ef4d7c5678f668 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Mon, 27 Jul 2026 04:31:56 +0000
Subject: [PATCH 2/2] fix: initialize `c_options` in the Stimulus type
 definition

The `PAGERANKOPT` type declares an optional `INOUT` argument,
so Stimulus wraps its input conversion into `if (!Rf_isNull(options))`,
but passes the pointer to `igraph_pagerank()` unconditionally.
Reading it when `options` is `NULL` at the R level is an uninitialized read,
flagged by `clang -Wsometimes-uninitialized`.

Declare the pointer with a `NULL` initializer via `CDECL`,
which is the same fix as in #2751 but applied to the code generator.
The `else` branch of the input conversion becomes redundant and is dropped,
so the default lives in one place only.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RF5eavxtBTfTSquRjc2San
---
 src/rinterface.c             |  6 ------
 tools/stimulus/types-RC.yaml | 12 ++++++++----
 2 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/src/rinterface.c b/src/rinterface.c
index 1ff2711494b..f74588cd392 100644
--- a/src/rinterface.c
+++ b/src/rinterface.c
@@ -5346,8 +5346,6 @@ SEXP R_igraph_pagerank(SEXP graph, SEXP algo, SEXP vids, SEXP directed, SEXP dam
     if (c_algo == IGRAPH_PAGERANK_ALGO_ARPACK) {
       Rz_SEXP_to_igraph_arpack_options(options, &c_options1);
       c_options = &c_options1;
-    } else {
-      c_options = NULL;
     }
   }
                                         /* Call igraph */
@@ -5422,8 +5420,6 @@ SEXP R_igraph_personalized_pagerank(SEXP graph, SEXP algo, SEXP vids, SEXP direc
     if (c_algo == IGRAPH_PAGERANK_ALGO_ARPACK) {
       Rz_SEXP_to_igraph_arpack_options(options, &c_options1);
       c_options = &c_options1;
-    } else {
-      c_options = NULL;
     }
   }
                                         /* Call igraph */
@@ -5497,8 +5493,6 @@ SEXP R_igraph_personalized_pagerank_vs(SEXP graph, SEXP algo, SEXP vids, SEXP di
     if (c_algo == IGRAPH_PAGERANK_ALGO_ARPACK) {
       Rz_SEXP_to_igraph_arpack_options(options, &c_options1);
       c_options = &c_options1;
-    } else {
-      c_options = NULL;
     }
   }
                                         /* Call igraph */
diff --git a/tools/stimulus/types-RC.yaml b/tools/stimulus/types-RC.yaml
index 7c362dba585..3d1ada36ec9 100644
--- a/tools/stimulus/types-RC.yaml
+++ b/tools/stimulus/types-RC.yaml
@@ -995,16 +995,20 @@ SIR_LIST:
             IGRAPH_FINALLY_CLEAN(1);
 
 PAGERANKOPT:
-    CTYPE: |-
+    CTYPE: void*
+    # The argument is optional,
+    # so the code generator wraps the input conversion into `if (!Rf_isNull(...))`.
+    # The pointer is passed on to igraph unconditionally,
+    # therefore it must be initialized here
+    # to stay well-defined on the path where the conversion is skipped.
+    CDECL: |-
       igraph_arpack_options_t %C%1;
-      void*
+      void* %C% = NULL;
     INCONV:
         INOUT: |-
           if (%C1% == IGRAPH_PAGERANK_ALGO_ARPACK) {
             Rz_SEXP_to_igraph_arpack_options(%I%, &%C%1);
             %C% = &%C%1;
-          } else {
-            %C% = NULL;
           }
     OUTCONV:
         INOUT: |-