test(android): Use volatile to produce SIGSEGV in native crash test (#4919)

* test(android): Use volatile to produce SIGSEGV in native crash test

The null-pointer dereference was undefined behavior that the compiler
optimized into a trap instruction, producing SIGILL (x86_64) or SIGTRAP
(arm64) instead of a real crash. Adding volatile forces an actual memory
access, resulting in a consistent SIGSEGV across architectures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* ci: Skip buildnative on runners with NO_MOBILE

The buildnative action builds Android-specific supplemental libraries
that are only needed by Sentry.Bindings.Android. On linux-arm64 and
other NO_MOBILE runners, the solution filter excludes that project,
so building native deps is unnecessary and fails (no Android NDK).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* ci: Fix JAVA_HOME_11 selection for ARM64 runners

Select JAVA_HOME_11 based on runner architecture instead of OS. The
previous check only used ARM64 for macOS, leaving Windows ARM64
with the empty X64 variant.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: jpnurmi

.github/actions/buildnative/action.yml

@@ -8,7 +8,7 @@ runs:
     - name: Set Environment Variables
       shell: bash
       run: |
-        if [[ "$RUNNER_OS" == "macOS" ]]; then
+        if [[ "$RUNNER_ARCH" == "ARM64" ]]; then
           echo "JAVA_HOME_11=$JAVA_HOME_11_ARM64" >> $GITHUB_ENV
         else
           echo "JAVA_HOME_11=$JAVA_HOME_11_X64" >> $GITHUB_ENV

.github/workflows/build.yml

@@ -197,7 +197,7 @@ jobs:
           enableCrossOsArchive: true
 
       - name: Build Native Dependencies
-        if: ${{ !matrix.container }}
+        if: ${{ !matrix.container && !env.NO_MOBILE }}
         uses: ./.github/actions/buildnative
 
       - name: Restore .NET Dependencies
@@ -372,6 +372,7 @@ jobs:
         uses: ./.github/actions/environment
 
       - name: Build Native Dependencies
+        if: ${{ !env.NO_MOBILE }}
         uses: ./.github/actions/buildnative
 
       - name: Fetch NuGet Packages

integration-test/android.Tests.ps1

@@ -162,7 +162,7 @@ Describe 'MAUI app (<dotnet_version>, <configuration>)' -ForEach $cases -Skip:(-
 
         Dump-ServerErrors -Result $result
         $result.HasErrors() | Should -BeFalse
-        $result.Events() | Should -AnyElementMatch "`"type`":`"SIG[A-Z]+`"" # SIGILL (x86_64), SIGTRAP (arm64-v8a)
+        $result.Events() | Should -AnyElementMatch "`"type`":`"SIGSEGV`""
         $result.Events() | Should -Not -AnyElementMatch "`"type`":`"System.\w+Exception`""
         $result.Events() | Should -HaveCount 1
     }

lib/sentrysupplemental/bin/arm64-v8a/libsentrysupplemental.so

@@ -1,6 +1,8 @@
 __attribute__((noinline))
 void crash()
 {
-    char *ptr = 0;
+    // volatile prevents the compiler from optimizing the null dereference (UB) into
+    // a trap instruction (SIGILL/SIGTRAP) and forces an actual SIGSEGV instead.
+    volatile char *ptr = 0;
     *ptr += 1;
 }