diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 293de8310..911a2e76c 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -178,7 +178,7 @@ jobs:
 
             ./configure CFLAGS="$CFLAGS_GCC_STYLE" --enable-jit --enable-pcre2-16 --enable-pcre2-32 --enable-Werror
             make -j3
-            make check
+            make check || (cat ./test-suite.log; false)
 
             make install "DESTDIR=`pwd`/install-dir"
             maint/RunManifestTest install-dir maint/manifest-makeinstall-freebsd
@@ -247,7 +247,7 @@ jobs:
 
             ./configure CC="cc -m32" CFLAGS="$CFLAGS_SOLARIS_CC" --enable-jit --enable-pcre2-16 --enable-pcre2-32 --enable-errwarn
             make
-            make check
+            make check || (cat ./test-suite.log; false)
 
             make install "DESTDIR=`pwd`/install-dir"
             maint/RunManifestTest install-dir maint/manifest-makeinstall-solaris
@@ -257,7 +257,7 @@ jobs:
 
             ./configure CC="cc -m64" CFLAGS="$CFLAGS_SOLARIS_CC" --enable-jit --enable-pcre2-16 --enable-pcre2-32 --enable-errwarn
             make
-            make check
+            make check || (cat ./test-suite.log; false)
 
             make install "DESTDIR=`pwd`/install-dir"
             maint/RunManifestTest install-dir maint/manifest-makeinstall-solaris
diff --git a/.github/workflows/dev.yml b/.github/workflows/dev.yml
index 5dc619654..0a9dea469 100644
--- a/.github/workflows/dev.yml
+++ b/.github/workflows/dev.yml
@@ -133,7 +133,7 @@ jobs:
         run: make -j3
 
       - name: Test
-        run: make check
+        run: make check || (cat ./test-suite.log; false)
 
       - name: Install
         run: |
@@ -331,6 +331,71 @@ jobs:
         shell: msys2 {0}
         run: cd build && ctest -j3 --output-on-failure
 
+  ptarmigan:
+    # Tests with various unusual processor architectures
+    name: Multiarch
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # S390x is important, because it's basically the only supported big-endian
+          # architecture I can find anywhere. I used to work on SPARC and PPC-be systems
+          # a long time ago, but even Debian has dropped those architectures now, so
+          # it's nice that there's *least one* arch remaining to shake out endian
+          # assumptions.
+          - arch: "s390x"
+            distro: ubuntu_latest
+          # Big-iron POWER only (this is not the PowerPC arch used in old Apple Macs)
+          - arch: "ppc64le"
+            distro: "ubuntu_latest"
+          # A 32-bit Linux build. i386 is mostly gone now, so ARMv7 is all that's left.
+          - arch: "armv7"
+            distro: "ubuntu_latest"
+          # The only really widely-deployed non-x86 archicture, at least that's likely
+          # to be running PCRE2.
+          - arch: "aarch64"
+            distro: "ubuntu_latest"
+          # Not used by anyone yet, really, but potentially the "next big thing".
+          - arch: "riscv64"
+            distro: "ubuntu_latest"
+    runs-on: ubuntu-24.04
+    permissions:
+      contents: read
+      packages: write # Necessary for uraimo/run-on-arch-action to use GitHub's Docker repository as a cache
+    if: github.event_name != 'pull_request'
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          submodules: true
+
+      - name: Prepare
+        run: ./autogen.sh
+
+      - uses: uraimo/run-on-arch-action@ac33288c3728ca72563c97b8b88dda5a65a84448 # v2.8.1
+        name: Configure, build, and test
+        with:
+          arch: ${{ matrix.arch }}
+          distro: ${{ matrix.distro }}
+
+          # Not required, but speeds up builds by storing container images in
+          # a GitHub package registry.
+          githubToken: ${{ github.token }}
+
+          env: | # YAML, but pipe character is necessary
+            CFLAGS_GCC_STYLE: ${{ env.CFLAGS_GCC_STYLE }}
+
+          install: |
+            apt-get -qq update
+            apt-get -qq install -y gcc cmake ninja-build zlib1g-dev libbz2-dev
+
+          run: |
+            set -e
+            # TODO: Set -DCMAKE_COMPILE_WARNING_AS_ERROR=ON (there's currently a build failure on S390x)
+            cmake -G Ninja -DPCRE2_SUPPORT_JIT=ON -DPCRE2_BUILD_PCRE2_16=ON -DPCRE2_BUILD_PCRE2_32=ON -DBUILD_SHARED_LIBS=ON -DBUILD_STATIC_LIBS=ON -DPCRE2_DEBUG=ON -DCMAKE_C_FLAGS="$CFLAGS_GCC_STYLE -Wno-format-truncation -Wno-format-overflow" -DCMAKE_COMPILE_WARNING_AS_ERROR=OFF -DCMAKE_BUILD_TYPE=RelWithDebInfo -B build
+            ninja -C build
+            (cd build && ctest -j3 --output-on-failure)
+
   zebrilus:
     # Tests with: Zig compiler
     name: Zig
diff --git a/src/pcre2_jit_char_inc.h b/src/pcre2_jit_char_inc.h
index 77652f69a..df04c48b7 100644
--- a/src/pcre2_jit_char_inc.h
+++ b/src/pcre2_jit_char_inc.h
@@ -1486,7 +1486,7 @@ static PCRE2_SPTR SLJIT_FUNC do_extuni_utf(jit_arguments *args, PCRE2_SPTR cc)
 {
 PCRE2_SPTR start_subject = args->begin;
 PCRE2_SPTR end_subject = args->end;
-int lgb, rgb, ricount;
+int lgb = 0, rgb, ricount;
 PCRE2_SPTR prevcc, endcc, bptr;
 BOOL first = TRUE;
 BOOL was_ep_ZWJ = FALSE;
@@ -1569,7 +1569,7 @@ static PCRE2_SPTR SLJIT_FUNC do_extuni_utf_invalid(jit_arguments *args, PCRE2_SP
 {
 PCRE2_SPTR start_subject = args->begin;
 PCRE2_SPTR end_subject = args->end;
-int lgb, rgb, ricount;
+int lgb = 0, rgb, ricount;
 PCRE2_SPTR prevcc, endcc, bptr;
 BOOL first = TRUE;
 BOOL was_ep_ZWJ = FALSE;
diff --git a/src/pcre2_jit_simd_inc.h b/src/pcre2_jit_simd_inc.h
index 66e93cd59..80f0ede99 100644
--- a/src/pcre2_jit_simd_inc.h
+++ b/src/pcre2_jit_simd_inc.h
@@ -1289,7 +1289,7 @@ if (char1 != char2)
 
 #else /* PCRE2_CODE_UNIT_WIDTH == 32 */
 
-for (int i = 0; i < 2; i++)
+for (i = 0; i < 2; i++)
   {
   replicate_imm_vector(compiler, i, cmp1_ind, char1 | bit, TMP1);
 
@@ -1483,7 +1483,7 @@ if (char1 != char2)
 
 #else /* PCRE2_CODE_UNIT_WIDTH == 32 */
 
-for (int i = 0; i < 2; i++)
+for (i = 0; i < 2; i++)
   {
   replicate_imm_vector(compiler, i, cmp1_ind, char1 | bit, TMP3);
 
@@ -1699,7 +1699,7 @@ if (char2a != char2b)
 
 #else /* PCRE2_CODE_UNIT_WIDTH == 32 */
 
-for (int i = 0; i < 2; i++)
+for (i = 0; i < 2; i++)
   {
   replicate_imm_vector(compiler, i, cmp1a_ind, char1a | bit1, TMP1);
 
diff --git a/src/pcre2test.c b/src/pcre2test.c
index 7b98aa954..fd74ffb1b 100644
--- a/src/pcre2test.c
+++ b/src/pcre2test.c
@@ -752,7 +752,7 @@ static modstruct modlist[] = {
   { "null_pattern",                MOD_PAT,  MOD_CTL, CTL2_NULL_PATTERN,          PO(control2) },
   { "null_replacement",            MOD_DAT,  MOD_CTL, CTL2_NULL_REPLACEMENT,      DO(control2) },
   { "null_subject",                MOD_DAT,  MOD_CTL, CTL2_NULL_SUBJECT,          DO(control2) },
-  { "offset",                      MOD_DAT,  MOD_INT, 0,                          DO(offset) },
+  { "offset",                      MOD_DAT,  MOD_SIZ, 0,                          DO(offset) },
   { "offset_limit",                MOD_CTM,  MOD_SIZ, 0,                          MO(offset_limit)},
   { "optimization_full",           MOD_CTC,  MOD_OPTMZ, PCRE2_OPTIMIZATION_FULL,  0 },
   { "optimization_none",           MOD_CTC,  MOD_OPTMZ, PCRE2_OPTIMIZATION_NONE,  0 },
@@ -776,7 +776,7 @@ static modstruct modlist[] = {
   { "start_optimize",              MOD_CTC,  MOD_OPTMZ, PCRE2_START_OPTIMIZE,     0 },
   { "start_optimize_off",          MOD_CTC,  MOD_OPTMZ, PCRE2_START_OPTIMIZE_OFF, 0 },
   { "startchar",                   MOD_PND,  MOD_CTL, CTL_STARTCHAR,              PO(control) },
-  { "startoffset",                 MOD_DAT,  MOD_INT, 0,                          DO(offset) },
+  { "startoffset",                 MOD_DAT,  MOD_SIZ, 0,                          DO(offset) },
   { "subject_literal",             MOD_PATP, MOD_CTL, CTL2_SUBJECT_LITERAL,       PO(control2) },
   { "substitute_callout",          MOD_PND,  MOD_CTL, CTL2_SUBSTITUTE_CALLOUT,    PO(control2) },
   { "substitute_case_callout",     MOD_PND,  MOD_CTL, CTL2_SUBSTITUTE_CASE_CALLOUT, PO(control2) },