raster: Handle realloc errors in unionFind.h

[ShubhamDesai]

Description
This pull request addresses two issues in r.terraflow/unionFind.h related to the use of realloc for memory reallocation. The changes ensure that memory is properly handled when realloc fails.

Issues
raster/r.terraflow/unionFind.h:129:9: error: Common realloc mistake: 'parent' nulled but not freed upon failure [memleakOnRealloc]
parent = (T *)realloc(parent, 2 * maxsize * sizeof(T));
^
raster/r.terraflow/unionFind.h:133:9: error: Common realloc mistake: 'rank' nulled but not freed upon failure [memleakOnRealloc]
rank = (T *)realloc(rank, 2 * maxsize * sizeof(T));

Changes Made

• Added temporary variables to store the results of realloc for parent and rank.
• Included checks to ensure that realloc succeeded before updating the original pointers.
• Implemented error handling to free the original memory if realloc fails.

[nilason]

Bear in mind this header file unionFind.h is a C++ file. This is how I would implement this (diff against main):

diff --git a/raster/r.terraflow/unionFind.h b/raster/r.terraflow/unionFind.h
index 698dcfc0c9..fdd084b4ae 100644
--- a/raster/r.terraflow/unionFind.h
+++ b/raster/r.terraflow/unionFind.h
@@ -20,10 +20,14 @@
 #define __UNION_FIND
 
 #include <assert.h>
-#include <stdlib.h>
-#include <string.h>
+#include <cstdlib>
+#include <cstring>
 #include <iostream>
 
+extern "C" {
+#include <grass/glocale.h>
+}
+
 /* initial range guesstimate */
 #define UNION_INITIAL_SIZE 2000
 
@@ -126,13 +130,21 @@ inline void unionFind<T>::makeSet(T x)
     if (x >= maxsize) {
         /* reallocate parent */
         cout << "UnionFind::makeSet: reallocate double " << maxsize << "\n";
-        parent = (T *)realloc(parent, 2 * maxsize * sizeof(T));
-        assert(parent);
-        memset(parent + maxsize, 0, maxsize * sizeof(T));
-        /*reallocate rank */
-        rank = (T *)realloc(rank, 2 * maxsize * sizeof(T));
-        assert(rank);
-        memset(rank + maxsize, 0, maxsize * sizeof(T));
+        if (void *new_parent = std::realloc(parent, 2 * maxsize * sizeof(T))) {
+            parent = static_cast<T *>(new_parent);
+            std::memset(parent + maxsize, 0, maxsize * sizeof(T));
+        }
+        else {
+            G_fatal_error(_("Not enough memory for %s"), "parent");
+        }
+        /* reallocate rank */
+        if (void *new_rank = std::realloc(rank, 2 * maxsize * sizeof(T))) {
+            rank = static_cast<T *>(new_rank);
+            std::memset(rank + maxsize, 0, maxsize * sizeof(T));
+        }
+        else {
+            G_fatal_error(_("Not enough memory for %s"), "rank");
+        }
         /*update maxsize */
         maxsize *= 2;
     }

Some notes why:

• #include <cstdlib> style include is preferred to#include <stdlib.h>
• C-style casting should be avoided, hence the static_cast
• G_fatal_error() is the GRASS way to "exit(EXIT_FAILURE)" with a message
• a string surrounded with _() will produce a localised string (with gettext)

[marisn]

a string surrounded with _() will produce a localised string (with gettext)

With the latest change to Weblate, I do not know how string extraction is done, but at least in our Make file strings from headers are not extracted

grass/locale/Makefile

Line 34 in 559e088

LIB_POTFILES = find ../lib \( -name "*.c" -o -name "*.py" \) | xargs grep -l "_(\"\|n_(\""

[nilason]

a string surrounded with _() will produce a localised string (with gettext)

With the latest change to Weblate, I do not know how string extraction is done, but at least in our Make file strings from headers are not extracted

grass/locale/Makefile

Line 34 in 559e088

LIB_POTFILES = find ../lib \( -name "*.c" -o -name "*.py" \) | xargs grep -l "_(\"\|n_(\""

Good point, but that is a completely separate issue.

[neteler]

(for the record: https://github.com/OSGeo/grass/blob/main/doc/infrastructure.md#user-message-translation-management-i18n )