From 461e8e369b5a695a687bea169127a600b798c4bc Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Wed, 8 Oct 2025 14:47:08 +0800
Subject: [PATCH 01/12] revert JVM options and CLASSPATH

---
 gradlew | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/gradlew b/gradlew
index 98a05d787ee04..e9ec4c1024da1 100755
--- a/gradlew
+++ b/gradlew
@@ -115,6 +115,8 @@ case "$( uname )" in                #(
 esac
 
 
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
 
 # Determine the Java command to use to start the JVM.
 if [ -n "$JAVA_HOME" ] ; then
@@ -171,6 +173,7 @@ fi
 # For Cygwin or MSYS, switch paths to Windows format before running java
 if "$cygwin" || "$msys" ; then
     APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
 
     JAVACMD=$( cygpath --unix "$JAVACMD" )
 
@@ -220,10 +223,13 @@ DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 #     and any embedded shellness will be escaped.
 #   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
 #     treated as '${Hostname}' itself on the command line.
-
+#
+# Before gradle 8.14 were not support using an executable JAR for the wrapper.
+# It causes a no main manifest attribute error if developers use the old wrapper.
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
-        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
         "$@"
 
 # Stop when "xargs" is not available.

From c0b0428457b6b9574a4e78c3845d4a4a264ab649 Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Wed, 8 Oct 2025 15:03:08 +0800
Subject: [PATCH 02/12] revise comments

---
 gradlew | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gradlew b/gradlew
index e9ec4c1024da1..18cd53e65fb3e 100755
--- a/gradlew
+++ b/gradlew
@@ -224,7 +224,7 @@ DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 #   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
 #     treated as '${Hostname}' itself on the command line.
 #
-# Before gradle 8.14 were not support using an executable JAR for the wrapper.
+# Before gradle 8.14 didn't support using an executable JAR for the wrapper.
 # It causes a no main manifest attribute error if developers use the old wrapper.
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \

From 002b8ca515672eeb08ac7fe7eca5bf7825dd130d Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Fri, 10 Oct 2025 15:35:40 +0800
Subject: [PATCH 03/12] Revert "revise comments"

This reverts commit c0b0428457b6b9574a4e78c3845d4a4a264ab649.
---
 gradlew | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gradlew b/gradlew
index 18cd53e65fb3e..e9ec4c1024da1 100755
--- a/gradlew
+++ b/gradlew
@@ -224,7 +224,7 @@ DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 #   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
 #     treated as '${Hostname}' itself on the command line.
 #
-# Before gradle 8.14 didn't support using an executable JAR for the wrapper.
+# Before gradle 8.14 were not support using an executable JAR for the wrapper.
 # It causes a no main manifest attribute error if developers use the old wrapper.
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \

From 199f8f9c9acde4c7bfb04642ca40f6183e9d3a77 Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Fri, 10 Oct 2025 15:35:54 +0800
Subject: [PATCH 04/12] Revert "revert JVM options and CLASSPATH"

This reverts commit 461e8e369b5a695a687bea169127a600b798c4bc.
---
 gradlew | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/gradlew b/gradlew
index e9ec4c1024da1..98a05d787ee04 100755
--- a/gradlew
+++ b/gradlew
@@ -115,8 +115,6 @@ case "$( uname )" in                #(
 esac
 
 
-CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
-
 
 # Determine the Java command to use to start the JVM.
 if [ -n "$JAVA_HOME" ] ; then
@@ -173,7 +171,6 @@ fi
 # For Cygwin or MSYS, switch paths to Windows format before running java
 if "$cygwin" || "$msys" ; then
     APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
-    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
 
     JAVACMD=$( cygpath --unix "$JAVACMD" )
 
@@ -223,13 +220,10 @@ DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 #     and any embedded shellness will be escaped.
 #   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
 #     treated as '${Hostname}' itself on the command line.
-#
-# Before gradle 8.14 were not support using an executable JAR for the wrapper.
-# It causes a no main manifest attribute error if developers use the old wrapper.
+
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
-        -classpath "$CLASSPATH" \
-        org.gradle.wrapper.GradleWrapperMain \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
         "$@"
 
 # Stop when "xargs" is not available.

From 3a0fe9715209748f9a4e43e13f154493f0d7dfdd Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Fri, 10 Oct 2025 17:43:51 +0800
Subject: [PATCH 05/12] verifying the version of wrapper jar

---
 gradlew        | 19 +++++++++++++++++++
 wrapper.gradle | 20 ++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/gradlew b/gradlew
index 98a05d787ee04..6d950375b45e3 100755
--- a/gradlew
+++ b/gradlew
@@ -201,6 +201,7 @@ fi
 
 
 # Loop in case we encounter an error.
+REQUIRED_WRAPPER_JAR_CHECKSUM=$(curl -sSL "https://services.gradle.org/distributions/gradle-9.1.0-wrapper.jar.sha256")
 for attempt in 1 2 3; do
   if [ ! -e "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" ]; then
     if ! curl -s -S --retry 3 -L -o "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" "https://raw.githubusercontent.com/gradle/gradle/v9.1.0/gradle/wrapper/gradle-wrapper.jar"; then
@@ -209,6 +210,24 @@ for attempt in 1 2 3; do
       sleep 5
       continue
     fi
+  else
+    # Verify checksum of existing wrapper JAR.
+    # Use sha256sum or shasum, whichever is available.
+    if command -v sha256sum >/dev/null 2>&1; then
+      LOCAL_WRAPPER_JAR_CHECKSUM=$(sha256sum "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" | awk '{print $1}')
+    elif command -v shasum >/dev/null 2>&1; then
+      LOCAL_WRAPPER_JAR_CHECKSUM=$(shasum -a 256 "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" | awk '{print $1}')
+    else
+      # If no checksum tool is found, delete the JAR and re-download.
+      warn "Cannot find sha256sum or shasum to verify wrapper JAR. Deleting and re-downloading."
+      rm -f "$APP_HOME/gradle/wrapper/gradle-wrapper.jar"
+      continue
+    fi
+
+    # If the local checksum does not match the required checksum, delete the JAR to force re-download.
+    if [ "$LOCAL_WRAPPER_JAR_CHECKSUM" != "$REQUIRED_WRAPPER_JAR_CHECKSUM" ] ; then
+      rm -f "$APP_HOME/gradle/wrapper/gradle-wrapper.jar"
+    fi
   fi
 done
 
diff --git a/wrapper.gradle b/wrapper.gradle
index 4cd9fc65f9d45..9bd5cd6ae271d 100644
--- a/wrapper.gradle
+++ b/wrapper.gradle
@@ -42,9 +42,11 @@ task bootstrapWrapper() {
         // fetch the jar.
         def wrapperBaseUrl = "https://raw.githubusercontent.com/gradle/gradle/v$versions.gradle/gradle/wrapper"
         def wrapperJarUrl = wrapperBaseUrl + "/gradle-wrapper.jar"
+        def wrapperJarChecksumUrl = "https://services.gradle.org/distributions/gradle-$versions.gradle-wrapper.jar.sha256"
 
         def bootstrapString = """
       # Loop in case we encounter an error.
+      REQUIRED_WRAPPER_JAR_CHECKSUM=\$(curl -sSL "$wrapperJarChecksumUrl")
       for attempt in 1 2 3; do
         if [ ! -e "$wrapperJarPath" ]; then
           if ! curl -s -S --retry 3 -L -o "$wrapperJarPath" "$wrapperJarUrl"; then
@@ -53,6 +55,24 @@ task bootstrapWrapper() {
             sleep 5
             continue
           fi
+        else
+          # Verify checksum of existing wrapper JAR.
+          # Use sha256sum or shasum, whichever is available.
+          if command -v sha256sum >/dev/null 2>&1; then
+            LOCAL_WRAPPER_JAR_CHECKSUM=\$(sha256sum "$wrapperJarPath" | awk '{print \$1}')
+          elif command -v shasum >/dev/null 2>&1; then
+            LOCAL_WRAPPER_JAR_CHECKSUM=\$(shasum -a 256 "$wrapperJarPath" | awk '{print \$1}')
+          else
+            # If no checksum tool is found, delete the JAR and re-download.
+            warn "Cannot find sha256sum or shasum to verify wrapper JAR. Deleting and re-downloading."
+            rm -f "$wrapperJarPath"
+            continue
+          fi
+
+          # If the local checksum does not match the required checksum, delete the JAR to force re-download.
+          if [ "\$LOCAL_WRAPPER_JAR_CHECKSUM" != "\$REQUIRED_WRAPPER_JAR_CHECKSUM" ] ; then
+            rm -f "$wrapperJarPath"
+          fi
         fi
       done
       """.stripIndent()

From 5c936800ecdd89e6cf46a209f19a361cdc2dd9ef Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Fri, 10 Oct 2025 20:42:50 +0800
Subject: [PATCH 06/12] hardcode required checksum and add comments

---
 gradlew        | 5 +++--
 wrapper.gradle | 8 +++++---
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/gradlew b/gradlew
index 6d950375b45e3..639977ca25997 100755
--- a/gradlew
+++ b/gradlew
@@ -201,7 +201,7 @@ fi
 
 
 # Loop in case we encounter an error.
-REQUIRED_WRAPPER_JAR_CHECKSUM=$(curl -sSL "https://services.gradle.org/distributions/gradle-9.1.0-wrapper.jar.sha256")
+REQUIRED_WRAPPER_JAR_CHECKSUM="76805e32c009c0cf0dd5d206bddc9fb22ea42e84db904b764f3047de095493f3"
 for attempt in 1 2 3; do
   if [ ! -e "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" ]; then
     if ! curl -s -S --retry 3 -L -o "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" "https://raw.githubusercontent.com/gradle/gradle/v9.1.0/gradle/wrapper/gradle-wrapper.jar"; then
@@ -211,7 +211,8 @@ for attempt in 1 2 3; do
       continue
     fi
   else
-    # Verify checksum of existing wrapper JAR.
+    # Verify checksum of existing wrapper JAR. 
+    # This prevents developers from running into incompatibility issues when using an outdated wrapper JAR after a Gradle upgrade.
     # Use sha256sum or shasum, whichever is available.
     if command -v sha256sum >/dev/null 2>&1; then
       LOCAL_WRAPPER_JAR_CHECKSUM=$(sha256sum "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" | awk '{print $1}')
diff --git a/wrapper.gradle b/wrapper.gradle
index 9bd5cd6ae271d..6ba1124aca94d 100644
--- a/wrapper.gradle
+++ b/wrapper.gradle
@@ -42,11 +42,12 @@ task bootstrapWrapper() {
         // fetch the jar.
         def wrapperBaseUrl = "https://raw.githubusercontent.com/gradle/gradle/v$versions.gradle/gradle/wrapper"
         def wrapperJarUrl = wrapperBaseUrl + "/gradle-wrapper.jar"
-        def wrapperJarChecksumUrl = "https://services.gradle.org/distributions/gradle-$versions.gradle-wrapper.jar.sha256"
+        // IMPORTANT: This checksum **must** be updated whenever the Gradle version changes.
+        String wrapperChecksum = "76805e32c009c0cf0dd5d206bddc9fb22ea42e84db904b764f3047de095493f3"
 
         def bootstrapString = """
       # Loop in case we encounter an error.
-      REQUIRED_WRAPPER_JAR_CHECKSUM=\$(curl -sSL "$wrapperJarChecksumUrl")
+      REQUIRED_WRAPPER_JAR_CHECKSUM="$wrapperChecksum"
       for attempt in 1 2 3; do
         if [ ! -e "$wrapperJarPath" ]; then
           if ! curl -s -S --retry 3 -L -o "$wrapperJarPath" "$wrapperJarUrl"; then
@@ -56,7 +57,8 @@ task bootstrapWrapper() {
             continue
           fi
         else
-          # Verify checksum of existing wrapper JAR.
+          # Verify checksum of existing wrapper JAR. 
+          # This prevents developers from running into incompatibility issues when using an outdated wrapper JAR after a Gradle upgrade.
           # Use sha256sum or shasum, whichever is available.
           if command -v sha256sum >/dev/null 2>&1; then
             LOCAL_WRAPPER_JAR_CHECKSUM=\$(sha256sum "$wrapperJarPath" | awk '{print \$1}')

From 673dab092f04dadcd843333c07a619a7eb94294d Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Sat, 11 Oct 2025 15:55:53 +0800
Subject: [PATCH 07/12] add break

---
 gradlew        | 2 ++
 wrapper.gradle | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/gradlew b/gradlew
index 639977ca25997..54d757905bff2 100755
--- a/gradlew
+++ b/gradlew
@@ -228,6 +228,8 @@ for attempt in 1 2 3; do
     # If the local checksum does not match the required checksum, delete the JAR to force re-download.
     if [ "$LOCAL_WRAPPER_JAR_CHECKSUM" != "$REQUIRED_WRAPPER_JAR_CHECKSUM" ] ; then
       rm -f "$APP_HOME/gradle/wrapper/gradle-wrapper.jar"
+    else
+      break
     fi
   fi
 done
diff --git a/wrapper.gradle b/wrapper.gradle
index 6ba1124aca94d..77e9aa887f6db 100644
--- a/wrapper.gradle
+++ b/wrapper.gradle
@@ -74,6 +74,8 @@ task bootstrapWrapper() {
           # If the local checksum does not match the required checksum, delete the JAR to force re-download.
           if [ "\$LOCAL_WRAPPER_JAR_CHECKSUM" != "\$REQUIRED_WRAPPER_JAR_CHECKSUM" ] ; then
             rm -f "$wrapperJarPath"
+          else
+            break
           fi
         fi
       done

From 1512bc93e99130b169c5872ac3491a2a37bdbf36 Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Mon, 13 Oct 2025 23:34:38 +0800
Subject: [PATCH 08/12] Adjust the handling method when there is no checksum
 tool

---
 gradlew        | 6 ++----
 wrapper.gradle | 6 ++----
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/gradlew b/gradlew
index 54d757905bff2..16d3eb6dbd584 100755
--- a/gradlew
+++ b/gradlew
@@ -219,10 +219,8 @@ for attempt in 1 2 3; do
     elif command -v shasum >/dev/null 2>&1; then
       LOCAL_WRAPPER_JAR_CHECKSUM=$(shasum -a 256 "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" | awk '{print $1}')
     else
-      # If no checksum tool is found, delete the JAR and re-download.
-      warn "Cannot find sha256sum or shasum to verify wrapper JAR. Deleting and re-downloading."
-      rm -f "$APP_HOME/gradle/wrapper/gradle-wrapper.jar"
-      continue
+      # If no checksum tool is found, exit with an error.
+      die "ERROR: Cannot find sha256sum or shasum to verify wrapper JAR. Please install one of these tools."
     fi
 
     # If the local checksum does not match the required checksum, delete the JAR to force re-download.
diff --git a/wrapper.gradle b/wrapper.gradle
index 77e9aa887f6db..4c271a6e5b7dd 100644
--- a/wrapper.gradle
+++ b/wrapper.gradle
@@ -65,10 +65,8 @@ task bootstrapWrapper() {
           elif command -v shasum >/dev/null 2>&1; then
             LOCAL_WRAPPER_JAR_CHECKSUM=\$(shasum -a 256 "$wrapperJarPath" | awk '{print \$1}')
           else
-            # If no checksum tool is found, delete the JAR and re-download.
-            warn "Cannot find sha256sum or shasum to verify wrapper JAR. Deleting and re-downloading."
-            rm -f "$wrapperJarPath"
-            continue
+            # If no checksum tool is found, exit with an error.
+            die "ERROR: Cannot find sha256sum or shasum to verify wrapper JAR. Please install one of these tools."
           fi
 
           # If the local checksum does not match the required checksum, delete the JAR to force re-download.

From 039e08cde00f2004b5107d1229ab9351be66cabc Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Tue, 14 Oct 2025 08:16:05 +0800
Subject: [PATCH 09/12] skip checksum if no tools

---
 gradlew        | 3 ++-
 wrapper.gradle | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/gradlew b/gradlew
index 16d3eb6dbd584..79876896bebf9 100755
--- a/gradlew
+++ b/gradlew
@@ -220,7 +220,8 @@ for attempt in 1 2 3; do
       LOCAL_WRAPPER_JAR_CHECKSUM=$(shasum -a 256 "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" | awk '{print $1}')
     else
       # If no checksum tool is found, exit with an error.
-      die "ERROR: Cannot find sha256sum or shasum to verify wrapper JAR. Please install one of these tools."
+      warn "Cannot find sha256sum or shasum to verify wrapper JAR."
+      break
     fi
 
     # If the local checksum does not match the required checksum, delete the JAR to force re-download.
diff --git a/wrapper.gradle b/wrapper.gradle
index 0473ef88d8154..ca53f2e19e2e1 100644
--- a/wrapper.gradle
+++ b/wrapper.gradle
@@ -65,7 +65,8 @@ task bootstrapWrapper() {
             LOCAL_WRAPPER_JAR_CHECKSUM=\$(shasum -a 256 "$wrapperJarPath" | awk '{print \$1}')
           else
             # If no checksum tool is found, exit with an error.
-            die "ERROR: Cannot find sha256sum or shasum to verify wrapper JAR. Please install one of these tools."
+            warn "Cannot find sha256sum or shasum to verify wrapper JAR."
+            break
           fi
 
           # If the local checksum does not match the required checksum, delete the JAR to force re-download.

From 3ab92f0760392f8f6ff51b77824b6a61886ae059 Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Fri, 17 Oct 2025 08:21:52 +0800
Subject: [PATCH 10/12] fix comments

---
 wrapper.gradle | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/wrapper.gradle b/wrapper.gradle
index ca53f2e19e2e1..bda27ab14349f 100644
--- a/wrapper.gradle
+++ b/wrapper.gradle
@@ -64,7 +64,7 @@ task bootstrapWrapper() {
           elif command -v shasum >/dev/null 2>&1; then
             LOCAL_WRAPPER_JAR_CHECKSUM=\$(shasum -a 256 "$wrapperJarPath" | awk '{print \$1}')
           else
-            # If no checksum tool is found, exit with an error.
+            # If no checksum tool is found, this verification is skipped .
             warn "Cannot find sha256sum or shasum to verify wrapper JAR."
             break
           fi

From 0bf201c15b8b061e2d82095f5d6d03284325f8b0 Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Fri, 17 Oct 2025 08:23:07 +0800
Subject: [PATCH 11/12] fix comments

---
 gradlew | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gradlew b/gradlew
index 79876896bebf9..2cb83c664d83c 100755
--- a/gradlew
+++ b/gradlew
@@ -219,7 +219,7 @@ for attempt in 1 2 3; do
     elif command -v shasum >/dev/null 2>&1; then
       LOCAL_WRAPPER_JAR_CHECKSUM=$(shasum -a 256 "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" | awk '{print $1}')
     else
-      # If no checksum tool is found, exit with an error.
+      # If no checksum tool is found, this verification is skipped .
       warn "Cannot find sha256sum or shasum to verify wrapper JAR."
       break
     fi

From 46989569b975dc06ba59983352027e035d7f43bd Mon Sep 17 00:00:00 2001
From: Chih-Yuan Chien <joshua2519@gmail.com>
Date: Fri, 17 Oct 2025 21:55:28 +0800
Subject: [PATCH 12/12] merge url and move checksum variable

---
 wrapper.gradle | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/wrapper.gradle b/wrapper.gradle
index bda27ab14349f..cd1de19c3d61a 100644
--- a/wrapper.gradle
+++ b/wrapper.gradle
@@ -39,10 +39,9 @@ task bootstrapWrapper() {
         // github.com servers deprecated TLSv1/TLSv1.1 support some time ago, so older versions
         // of curl (built against OpenSSL library that doesn't support TLSv1.2) would fail to
         // fetch the jar.
-        def wrapperBaseUrl = "https://raw.githubusercontent.com/gradle/gradle/v$versions.gradle/gradle/wrapper"
-        def wrapperJarUrl = wrapperBaseUrl + "/gradle-wrapper.jar"
         // IMPORTANT: This checksum **must** be updated whenever the Gradle version changes.
         String wrapperChecksum = "76805e32c009c0cf0dd5d206bddc9fb22ea42e84db904b764f3047de095493f3"
+        def wrapperJarUrl = "https://raw.githubusercontent.com/gradle/gradle/v$versions.gradle/gradle/wrapper/gradle-wrapper.jar"
 
         def bootstrapString = """
       # Loop in case we encounter an error.