commit 772b282a4e858a27af610bcdcc8b66925cbf1a83
Author: Tomas Korbar <tkorbar@redhat.com>
Date:   Tue Feb 28 16:08:13 2023 +0100

    avoid GCC code analysis bug

diff --git a/agen5/defLoad.c b/agen5/defLoad.c
index 0215857..b687263 100644
--- a/agen5/defLoad.c
+++ b/agen5/defLoad.c
@@ -448,17 +448,28 @@ read_defs(void)
     FILE *        fp;
     def_input_mode_t in_mode = ready_def_input(&def_fname, &data_sz);
 
+    /*
+     * "ready_def_input" has a lot of side effects. It's possible that
+     * there are no definitions, so "in_mode" is set to DONE and there's
+     * nothing to do.
+     */
     if (in_mode == INPUT_DONE)
         return;
 
     /*
      *  Allocate the space we need for our definitions.
+     * "data_sz" was set by read_def_input to the size of the
+     * definitions file (or 4096 if we're reading from a fifo file).
+     * In that alternate case, we'll start the input size at 4096 bytes.
+     * The allocation includes space for context and a NUL byte or two
      */
-    rem_sz = data_sz+4+sizeof(*base_ctx);
-    base_ctx = (scan_ctx_t *)AGALOC(rem_sz, "file buf");
-    memset(VOIDP(base_ctx), 0, rem_sz);
+    {
+        size_t sz = data_sz + sizeof(long) + sizeof(*base_ctx);
+        base_ctx = (scan_ctx_t *)AGALOC(sz, "file buf");
+        memset(VOIDP(base_ctx), 0, sz);
+    }
     base_ctx->scx_line = 1;
-    rem_sz = data_sz;
+    rem_sz = data_sz; // size available for storing def text
 
     /*
      *  Our base context will have its currency pointer set to this
@@ -482,6 +493,9 @@ read_defs(void)
         if (fp == NULL)
             AG_CANT(READ_DEF_OPEN, def_fname);
 
+        /*
+         * If we're emitting dependency information, then do so.
+         */
         if (dep_fp != NULL)
             add_source_file(def_fname);
     }
@@ -516,8 +530,7 @@ read_defs(void)
          *  See if there is any space left
          */
         if (rem_sz == 0) {
-            scan_ctx_t * p;
-            off_t dataOff;
+            off_t scan_off;
 
             /*
              *  IF it is a regular file, then we are done
@@ -527,24 +540,16 @@ read_defs(void)
 
             /*
              *  We have more data and we are out of space.
-             *  Try to reallocate our input buffer.
+             *  AGREALOC will succeed or not return.
              */
             data_sz += (rem_sz = 0x1000);
-            dataOff = data - base_ctx->scx_data;
-            p = AGREALOC(VOIDP(base_ctx), data_sz + 4 + sizeof(*base_ctx),
-                         "expand f buf");
+            scan_off = data - base_ctx->scx_data;
+            base_ctx = AGREALOC(VOIDP(base_ctx), data_sz + 4 + sizeof(*base_ctx),
+                                "expand f buf");
 
-            /*
-             *  The buffer may have moved.  Set the data pointer at an
-             *  offset within the new buffer and make sure our base pointer
-             *  has been corrected as well.
-             */
-            if (p != base_ctx) {
-                p->scx_scan = \
-                    p->scx_data = (char *)(p + 1);
-                data = p->scx_data + dataOff;
-                base_ctx = p;
-            }
+            base_ctx->scx_scan = \
+                base_ctx->scx_data = (char *)(base_ctx + 1);
+            data = base_ctx->scx_data + scan_off;
         }
     }