diff --git a/cpp/src/gandiva/gdv_function_stubs_test.cc b/cpp/src/gandiva/gdv_function_stubs_test.cc
index cbe24b74236f..a423d8dd85d7 100644
--- a/cpp/src/gandiva/gdv_function_stubs_test.cc
+++ b/cpp/src/gandiva/gdv_function_stubs_test.cc
@@ -21,6 +21,8 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
+#include <limits>
+
 #include "arrow/util/logging.h"
 #include "gandiva/execution_context.h"
 
@@ -526,6 +528,21 @@ TEST(TestGdvFnStubs, TestSubstringIndex) {
   out_str = gdv_fn_substring_index(ctx_ptr, "路学\\L", 8, "\\", 1, -1, &out_len);
   EXPECT_EQ(std::string(out_str, out_len), "L");
   EXPECT_FALSE(ctx.has_error());
+
+  // Large counts return full string when delimiter not found enough times
+  out_str = gdv_fn_substring_index(ctx_ptr, "a.b.c", 5, ".", 1, -1000, &out_len);
+  EXPECT_EQ(std::string(out_str, out_len), "a.b.c");
+  EXPECT_FALSE(ctx.has_error());
+
+  out_str = gdv_fn_substring_index(ctx_ptr, "a.b.c", 5, ".", 1,
+                                   std::numeric_limits<int32_t>::max(), &out_len);
+  EXPECT_EQ(std::string(out_str, out_len), "a.b.c");
+  EXPECT_FALSE(ctx.has_error());
+
+  out_str = gdv_fn_substring_index(ctx_ptr, "a.b.c", 5, ".", 1,
+                                   std::numeric_limits<int32_t>::min(), &out_len);
+  EXPECT_EQ(std::string(out_str, out_len), "a.b.c");
+  EXPECT_FALSE(ctx.has_error());
 }
 
 TEST(TestGdvFnStubs, TestUpper) {
diff --git a/cpp/src/gandiva/gdv_string_function_stubs.cc b/cpp/src/gandiva/gdv_string_function_stubs.cc
index e7982461b439..4e62d24a7b2c 100644
--- a/cpp/src/gandiva/gdv_string_function_stubs.cc
+++ b/cpp/src/gandiva/gdv_string_function_stubs.cc
@@ -407,14 +407,17 @@ const char* gdv_fn_substring_index(int64_t context, const char* txt, int32_t txt
     }
   }
 
-  if (static_cast<int32_t>(abs(cnt)) <= static_cast<int32_t>(occ.size()) && cnt > 0) {
+  // Use int64_t to avoid undefined behavior with abs(INT_MIN)
+  int64_t abs_cnt = (cnt < 0) ? -static_cast<int64_t>(cnt) : static_cast<int64_t>(cnt);
+  int64_t occ_size = static_cast<int64_t>(occ.size());
+
+  if (abs_cnt <= occ_size && cnt > 0) {
     memcpy(out, txt, occ[cnt - 1]);
     *out_len = occ[cnt - 1];
     return out;
-  } else if (static_cast<int32_t>(abs(cnt)) <= static_cast<int32_t>(occ.size()) &&
-             cnt < 0) {
+  } else if (abs_cnt <= occ_size && cnt < 0) {
     int32_t sz = static_cast<int32_t>(occ.size());
-    int32_t temp = static_cast<int32_t>(abs(cnt));
+    int32_t temp = static_cast<int32_t>(abs_cnt);
 
     memcpy(out, txt + occ[sz - temp] + pat_len, txt_len - occ[sz - temp] - pat_len);
     *out_len = txt_len - occ[sz - temp] - pat_len;
diff --git a/cpp/src/gandiva/precompiled/extended_math_ops.cc b/cpp/src/gandiva/precompiled/extended_math_ops.cc
index b2562e955acd..c29f8f2a8684 100644
--- a/cpp/src/gandiva/precompiled/extended_math_ops.cc
+++ b/cpp/src/gandiva/precompiled/extended_math_ops.cc
@@ -386,16 +386,22 @@ gdv_int64 get_power_of_10(gdv_int32 exp) {
 
 FORCE_INLINE
 gdv_int64 truncate_int64_int32(gdv_int64 in, gdv_int32 out_scale) {
+  // For int64 (no fractional digits), positive scale is a no-op
+  if (out_scale >= 0) {
+    return in;
+  }
+  // GetScaleMultiplier only supports scales 0-38
+  if (out_scale < -38) {
+    return 0;
+  }
+
   bool overflow = false;
   arrow::BasicDecimal128 decimal = gandiva::decimalops::FromInt64(in, 38, 0, &overflow);
   arrow::BasicDecimal128 decimal_with_outscale =
       gandiva::decimalops::Truncate(gandiva::BasicDecimalScalar128(decimal, 38, 0), 38,
                                     out_scale, out_scale, &overflow);
-  if (out_scale < 0) {
-    out_scale = 0;
-  }
   return gandiva::decimalops::ToInt64(
-      gandiva::BasicDecimalScalar128(decimal_with_outscale, 38, out_scale), &overflow);
+      gandiva::BasicDecimalScalar128(decimal_with_outscale, 38, 0), &overflow);
 }
 
 FORCE_INLINE
diff --git a/cpp/src/gandiva/precompiled/extended_math_ops_test.cc b/cpp/src/gandiva/precompiled/extended_math_ops_test.cc
index 7170fad01d25..ad0cb78188c5 100644
--- a/cpp/src/gandiva/precompiled/extended_math_ops_test.cc
+++ b/cpp/src/gandiva/precompiled/extended_math_ops_test.cc
@@ -22,6 +22,7 @@
 #include <gtest/gtest.h>
 
 #include <cmath>
+#include <limits>
 
 #include "gandiva/execution_context.h"
 #include "gandiva/precompiled/types.h"
@@ -208,6 +209,18 @@ TEST(TestExtendedMathOps, TestTruncate) {
   EXPECT_EQ(truncate_int64_int32(-1234, -2), -1200);
   EXPECT_EQ(truncate_int64_int32(8124674407369523212, 0), 8124674407369523212);
   EXPECT_EQ(truncate_int64_int32(8124674407369523212, -2), 8124674407369523200);
+
+  // Positive scales are no-op for int64 (no fractional digits)
+  EXPECT_EQ(truncate_int64_int32(12345, std::numeric_limits<int32_t>::max()), 12345);
+  EXPECT_EQ(truncate_int64_int32(-12345, std::numeric_limits<int32_t>::max()), -12345);
+  EXPECT_EQ(truncate_int64_int32(12345, 100), 12345);
+  EXPECT_EQ(truncate_int64_int32(12345, 39), 12345);
+
+  // Scales beyond [-38, 0) truncate all digits
+  EXPECT_EQ(truncate_int64_int32(12345, std::numeric_limits<int32_t>::min()), 0);
+  EXPECT_EQ(truncate_int64_int32(12345, -100), 0);
+  EXPECT_EQ(truncate_int64_int32(12345, -39), 0);
+  EXPECT_EQ(truncate_int64_int32(-99999, -39), 0);
 }
 
 TEST(TestExtendedMathOps, TestTrigonometricFunctions) {