diff --git a/.github/workflows/checks.yaml b/.github/workflows/checks.yaml
index a70ba478..b574ba7b 100644
--- a/.github/workflows/checks.yaml
+++ b/.github/workflows/checks.yaml
@@ -87,11 +87,21 @@ jobs:
         run: cargo nextest run --target ${{matrix.target}} ${{ matrix.features }} --no-fail-fast
         env:
           RUST_BACKTRACE: 1
+      - name: cargo nextest cdylib
+        if: matrix.os != 'windows-2022'
+        working-directory: libz-rs-sys-cdylib
+        run: cargo llvm-cov nextest --target ${{matrix.target}} ${{ matrix.features }} --features="gz,__internal-test" --lcov --output-path cdylib.lcov.info --ignore-filename-regex "test-libz|dynamic-libz"
+      - name: cargo nextest cdylib
+        if: matrix.os == 'windows-2022'
+        working-directory: libz-rs-sys-cdylib
+        run: cargo nextest run --target ${{matrix.target}} ${{ matrix.features }} --features="gz,__internal-test" --no-fail-fast
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@0565863a31f2c772f9f0395002a31e3f06189574 # v5.4.0
         if: matrix.os != 'windows-2022' && matrix.rust == 'stable'
         with:
-          files: ./lcov.info
+          files: |
+            ./lcov.info
+            ./cdylib.lcov.info
           fail_ci_if_error: false
           flags: test-${{matrix.target}}
           token: ${{ secrets.CODECOV_TOKEN }}
@@ -167,15 +177,22 @@ jobs:
         uses: dtolnay/rust-toolchain@be73d7920c329f220ce78e0234b8f96b7ae60248
         with:
           toolchain: stable
-          components: clippy
+          components: clippy, rustfmt
           targets: ${{matrix.target}}
       - name: Rust cache
         uses: Swatinem/rust-cache@3cf7f8cc28d1b4e7d01e3783be10a97d55d483c8
         with:
             shared-key: "stable-${{matrix.target}}"
 
-      - name: Run clippy
-        run: cargo clippy --target ${{matrix.target}} ${{matrix.features}} --workspace --all-targets -- -D warnings
+      - name: Run rustfmt and clippy
+        run: |
+          cargo fmt --all --check
+          cargo clippy --target ${{matrix.target}} ${{matrix.features}} --workspace --all-targets -- -D warnings
+      - name: Run rustfmt and clippy (cdylib)
+        working-directory: libz-rs-sys-cdylib
+        run: |
+          cargo fmt --all --check
+          cargo clippy --target ${{matrix.target}} ${{matrix.features}} --workspace --all-targets -- -D warnings
       - name: Run clippy (fuzzers)
         if: ${{ !contains(matrix.features, 'gz') }}
         run: cargo clippy --target ${{matrix.target}} ${{matrix.features}} --manifest-path ./fuzz/Cargo.toml --all-targets -- -D warnings
@@ -255,7 +272,7 @@ jobs:
           done
 
   fuzz-code-coverage:
-    name: Fuzz with code coverage 
+    name: Fuzz with code coverage
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -399,7 +416,7 @@ jobs:
         working-directory: libz-rs-sys-cdylib
         run: |
           # build using cargo-c this time
-          cargo cinstall --offline --release --destdir=/tmp/cargo-cbuild-libz-rs
+          cargo cinstall --release --destdir=/tmp/cargo-cbuild-libz-rs
           tree /tmp/cargo-cbuild-libz-rs
           # verify that the SONAME  is set and includes a version
           objdump -p target/x86_64-unknown-linux-gnu/release/libz_rs.so | awk '/SONAME/{print $2}' | grep -E 'libz_rs\.so\.1'
@@ -483,7 +500,8 @@ jobs:
       - name: Test allocator with miri
         run: "cargo +nightly miri nextest run -j4 -p zlib-rs --target ${{ matrix.target }} allocate::"
       - name: Test gz logic with miri
-        run: "cargo +nightly miri nextest run -j4 -p libz-rs-sys --target ${{ matrix.target }} --features=gz"
+        working-directory: libz-rs-sys-cdylib
+        run: "cargo +nightly miri nextest run -j4 -p libz-rs-sys-cdylib --target ${{ matrix.target }} --features=gz"
         env:
           MIRIFLAGS: "-Zmiri-tree-borrows -Zmiri-disable-isolation"
 
diff --git a/Cargo.lock b/Cargo.lock
index 158f6118..04839818 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -132,8 +132,16 @@ dependencies = [
 [[package]]
 name = "libz-rs-sys"
 version = "0.5.0"
+dependencies = [
+ "zlib-rs",
+]
+
+[[package]]
+name = "libz-rs-sys-cdylib"
+version = "0.5.0"
 dependencies = [
  "libc",
+ "libz-rs-sys",
  "zlib-rs",
 ]
 
@@ -280,6 +288,7 @@ dependencies = [
  "libc",
  "libloading",
  "libz-rs-sys",
+ "libz-rs-sys-cdylib",
  "libz-sys",
  "quickcheck",
  "tempfile",
diff --git a/libz-rs-sys-cdylib/Cargo.lock b/libz-rs-sys-cdylib/Cargo.lock
index 30a537f2..79e94b7d 100644
--- a/libz-rs-sys-cdylib/Cargo.lock
+++ b/libz-rs-sys-cdylib/Cargo.lock
@@ -2,6 +2,12 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "libc"
+version = "0.2.172"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d750af042f7ef4f724306de029d18836c26c1765a54a6a3f094cbd23a7267ffa"
+
 [[package]]
 name = "libz-rs-sys"
 version = "0.5.0"
@@ -13,7 +19,9 @@ dependencies = [
 name = "libz-rs-sys-cdylib"
 version = "0.5.0"
 dependencies = [
+ "libc",
  "libz-rs-sys",
+ "zlib-rs",
 ]
 
 [[package]]
diff --git a/libz-rs-sys-cdylib/Cargo.toml b/libz-rs-sys-cdylib/Cargo.toml
index e3df2cdf..b55ce489 100644
--- a/libz-rs-sys-cdylib/Cargo.toml
+++ b/libz-rs-sys-cdylib/Cargo.toml
@@ -12,8 +12,7 @@ rust-version = "1.75" # MSRV
 
 [lib]
 name = "z_rs" # turns into e.g. `libz_rs.so`
-crate-type=["cdylib"]
-test = false
+crate-type = ["cdylib", "lib"]
 
 [profile.dev]
 panic = "abort" # abort on panics. This is crucial, unwinding would cause UB!
@@ -28,9 +27,13 @@ rust-allocator = ["libz-rs-sys/rust-allocator", "libz-rs-sys/std"] # by default,
 custom-prefix = ["libz-rs-sys/custom-prefix"] # use the LIBZ_RS_SYS_PREFIX to prefix all exported symbols
 semver-prefix = ["libz-rs-sys/semver-prefix"] # prefix all symbols in a semver-compatible way
 capi = []
+gz = ["dep:libc"] # support for the `gz*` functions is experimental
+__internal-test = []
 
 [dependencies]
 libz-rs-sys = { version = "0.5.0", path = "../libz-rs-sys", default-features = false, features = ["export-symbols"] }
+zlib-rs = { version = "0.5.0", path = "../zlib-rs", default-features = false }
+libc = { version = "0.2.171", optional = true }
 
 [package.metadata.capi.library]
 version = "1.3.0" # the zlib api version we match
diff --git a/libz-rs-sys/src/gz.rs b/libz-rs-sys-cdylib/src/gz.rs
similarity index 97%
rename from libz-rs-sys/src/gz.rs
rename to libz-rs-sys-cdylib/src/gz.rs
index 5be94045..22d46547 100644
--- a/libz-rs-sys/src/gz.rs
+++ b/libz-rs-sys-cdylib/src/gz.rs
@@ -5,8 +5,8 @@ pub use zlib_rs::c_api::*;
 
 use crate::gz::GzMode::GZ_READ;
 use crate::{
-    deflate, deflateEnd, deflateInit2_, deflateReset, inflate, inflateEnd, inflateInit2,
-    inflateReset, z_off_t, zlibVersion,
+    deflate, deflateEnd, deflateInit2_, deflateReset, inflate, inflateEnd, inflateInit2_,
+    inflateReset, z_off_t, z_stream, zlibVersion,
 };
 use core::ffi::{c_char, c_int, c_uint, c_void, CStr};
 use core::ptr;
@@ -22,9 +22,11 @@ use zlib_rs::MAX_WBITS;
 /// of an open gzFile to support the gzgetc() C macro. Since Rust code won't be
 /// using that C macro, we define gzFile_s as an empty structure. The first fields
 /// in GzState match what would be in the C version of gzFile_s.
+#[allow(non_camel_case_types)]
 pub enum gzFile_s {}
 
 /// File handle for an open gzip file.
+#[allow(non_camel_case_types)]
 pub type gzFile = *mut gzFile_s;
 
 // The internals of a gzip file handle (the thing gzFile actually points to, with the
@@ -139,6 +141,7 @@ impl GzState {
 
 // Gzip operating modes
 // NOTE: These values match what zlib-ng uses.
+#[allow(non_camel_case_types)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 enum GzMode {
     GZ_NONE = 0,
@@ -186,7 +189,9 @@ enum Source {
 ///
 /// The caller must ensure that `path` and `mode` point to valid C strings. If the
 /// return value is non-NULL, caller must delete it using only [`gzclose`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzopen))]
+///
+/// [`gzfree`]: crate::z_stream
+#[export_name = crate::prefix!(gzopen)]
 pub unsafe extern "C-unwind" fn gzopen(path: *const c_char, mode: *const c_char) -> gzFile {
     if path.is_null() {
         return ptr::null_mut();
@@ -208,7 +213,9 @@ pub unsafe extern "C-unwind" fn gzopen(path: *const c_char, mode: *const c_char)
 ///
 /// The caller must ensure that `mode` points to a valid C string. If the
 /// return value is non-NULL, caller must delete it using only [`gzclose`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzdopen))]
+///
+/// [`gzfree`]: crate::z_stream
+#[export_name = crate::prefix!(gzdopen)]
 pub unsafe extern "C-unwind" fn gzdopen(fd: c_int, mode: *const c_char) -> gzFile {
     // Safety: the caller is responsible for `mode` being a non-null C string.
     unsafe { gzopen_help(Source::Fd(fd), mode) }
@@ -360,9 +367,6 @@ fn fd_path(buf: &mut [u8; 27], fd: c_int) -> &CStr {
     // characters, plus space for the largest decimal value for the `c_int` type. On some systems
     // the c_int type can actually be 64 bits. The `i64::MIN` value has 20 digits, and the minus
     // sign, for a total of 6 + 20 + 1 = 27.
-    #[cfg(feature = "std")]
-    debug_assert!(format!("<fd:{}>\0", i64::MIN).len() <= buf.len());
-
     struct Writer<'a> {
         buf: &'a mut [u8; 27],
         len: usize,
@@ -551,7 +555,7 @@ unsafe fn deallocate_cstr(s: *mut c_char) {
 ///
 /// `file` must not be used after this call returns, as the memory it references may have
 /// been deallocated.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzclose))]
+#[export_name = crate::prefix!(gzclose)]
 pub unsafe extern "C-unwind" fn gzclose(file: gzFile) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_ref() }) else {
         return Z_STREAM_ERROR;
@@ -578,7 +582,7 @@ pub unsafe extern "C-unwind" fn gzclose(file: gzFile) -> c_int {
 ///
 /// `file` must not be used after this call returns, as the memory it references may have
 /// been deallocated.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzclose_r))]
+#[export_name = crate::prefix!(gzclose_r)]
 pub unsafe extern "C-unwind" fn gzclose_r(file: gzFile) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return Z_STREAM_ERROR;
@@ -627,7 +631,7 @@ pub unsafe extern "C-unwind" fn gzclose_r(file: gzFile) -> c_int {
 ///
 /// `file` must not be used after this call returns, as the memory it references may have
 /// been deallocated.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzclose_w))]
+#[export_name = crate::prefix!(gzclose_w)]
 pub unsafe extern "C-unwind" fn gzclose_w(file: gzFile) -> c_int {
     let mut ret = Z_OK;
 
@@ -689,7 +693,7 @@ pub unsafe extern "C-unwind" fn gzclose_w(file: gzFile) -> c_int {
 /// `file` must be one of the following:
 /// - A file handle must have been obtained from a function in this library, such as [`gzopen`].
 /// - A null pointer.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzbuffer))]
+#[export_name = crate::prefix!(gzbuffer)]
 pub unsafe extern "C-unwind" fn gzbuffer(file: gzFile, size: c_uint) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
@@ -748,7 +752,7 @@ pub unsafe extern "C-unwind" fn gzbuffer(file: gzFile, size: c_uint) -> c_int {
 /// deallocate the string.
 ///
 /// If `errnum` is non-null, it must point to an address at which a [`c_int`] may be written.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzerror))]
+#[export_name = crate::prefix!(gzerror)]
 pub unsafe extern "C-unwind" fn gzerror(file: gzFile, errnum: *mut c_int) -> *const c_char {
     // Get internal structure and check integrity
     let Some(state) = (unsafe { file.cast::<GzState>().as_ref() }) else {
@@ -784,7 +788,7 @@ pub unsafe extern "C-unwind" fn gzerror(file: gzFile, errnum: *mut c_int) -> *co
 /// # Safety
 ///
 /// `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzclearerr))]
+#[export_name = crate::prefix!(gzclearerr)]
 pub unsafe extern "C-unwind" fn gzclearerr(file: gzFile) {
     // Get internal structure and check integrity
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
@@ -821,7 +825,7 @@ pub unsafe extern "C-unwind" fn gzclearerr(file: gzFile) {
 /// # Safety
 ///
 /// `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzeof))]
+#[export_name = crate::prefix!(gzeof)]
 pub unsafe extern "C-unwind" fn gzeof(file: gzFile) -> c_int {
     // Get internal structure and check integrity
     let Some(state) = (unsafe { file.cast::<GzState>().as_ref() }) else {
@@ -861,7 +865,7 @@ pub unsafe extern "C-unwind" fn gzeof(file: gzFile) -> c_int {
 /// # Safety
 ///
 /// `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzdirect))]
+#[export_name = crate::prefix!(gzdirect)]
 pub unsafe extern "C-unwind" fn gzdirect(file: gzFile) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return 0;
@@ -920,7 +924,7 @@ pub unsafe extern "C-unwind" fn gzdirect(file: gzFile) -> c_int {
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
 /// - The caller must ensure that `buf` points to at least `len` writable bytes.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzread))]
+#[export_name = crate::prefix!(gzread)]
 pub unsafe extern "C-unwind" fn gzread(file: gzFile, buf: *mut c_void, len: c_uint) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
@@ -980,7 +984,7 @@ pub unsafe extern "C-unwind" fn gzread(file: gzFile, buf: *mut c_void, len: c_ui
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
 /// - The caller must ensure that `buf` points to at least `size * nitems` writable bytes.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzfread))]
+#[export_name = crate::prefix!(gzfread)]
 pub unsafe extern "C-unwind" fn gzfread(
     buf: *mut c_void,
     size: size_t,
@@ -1207,7 +1211,15 @@ unsafe fn gz_look(state: &mut GzState) -> Result<(), ()> {
         state.stream.next_in = ptr::null_mut();
         // Safety: `gzopen_help` initialized `state.stream`'s `zalloc`, `zfree`, and
         // `opaque` fields as needed by `inflateInit2`.
-        if unsafe { inflateInit2(&mut state.stream as *mut z_stream, MAX_WBITS + 16) } != Z_OK {
+        if unsafe {
+            inflateInit2_(
+                &mut state.stream as *mut z_stream,
+                MAX_WBITS + 16,
+                zlibVersion(),
+                std::mem::size_of::<z_stream>() as i32,
+            )
+        } != Z_OK
+        {
             // Safety: The caller confirmed the validity of `state`, and `free_buffers` checks
             // for null input and output pointers internally.
             unsafe { free_buffers(state) };
@@ -1478,7 +1490,7 @@ unsafe fn gz_decomp(state: &mut GzState) -> Result<(), ()> {
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
 /// - `buf` must point to at least `len` bytes of readable memory.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzwrite))]
+#[export_name = crate::prefix!(gzwrite)]
 pub unsafe extern "C-unwind" fn gzwrite(file: gzFile, buf: *const c_void, len: c_uint) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return 0;
@@ -1527,7 +1539,7 @@ pub unsafe extern "C-unwind" fn gzwrite(file: gzFile, buf: *const c_void, len: c
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
 /// - The caller must ensure that `buf` points to at least `size * nitems` readable bytes.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzfwrite))]
+#[export_name = crate::prefix!(gzfwrite)]
 pub unsafe extern "C-unwind" fn gzfwrite(
     buf: *const c_void,
     size: size_t,
@@ -1863,7 +1875,7 @@ fn gz_comp(state: &mut GzState, flush: c_int) -> Result<(), ()> {
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzflush))]
+#[export_name = crate::prefix!(gzflush)]
 pub unsafe extern "C-unwind" fn gzflush(file: gzFile, flush: c_int) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return Z_STREAM_ERROR;
@@ -1906,7 +1918,7 @@ pub unsafe extern "C-unwind" fn gzflush(file: gzFile, flush: c_int) -> c_int {
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gztell))]
+#[export_name = crate::prefix!(gztell)]
 pub unsafe extern "C-unwind" fn gztell(file: gzFile) -> z_off_t {
     let Some(state) = (unsafe { file.cast::<GzState>().as_ref() }) else {
         return -1;
@@ -1940,7 +1952,7 @@ pub unsafe extern "C-unwind" fn gztell(file: gzFile) -> z_off_t {
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzoffset))]
+#[export_name = crate::prefix!(gzoffset)]
 pub unsafe extern "C-unwind" fn gzoffset(file: gzFile) -> z_off_t {
     let Some(state) = (unsafe { file.cast::<GzState>().as_ref() }) else {
         return -1;
@@ -1975,7 +1987,7 @@ pub unsafe extern "C-unwind" fn gzoffset(file: gzFile) -> z_off_t {
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzputc))]
+#[export_name = crate::prefix!(gzputc)]
 pub unsafe extern "C-unwind" fn gzputc(file: gzFile, c: c_int) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
@@ -2033,7 +2045,7 @@ pub unsafe extern "C-unwind" fn gzputc(file: gzFile, c: c_int) -> c_int {
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
 /// - `s` must point to a null-terminated C string.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzputs))]
+#[export_name = crate::prefix!(gzputs)]
 pub unsafe extern "C-unwind" fn gzputs(file: gzFile, s: *const c_char) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
@@ -2075,7 +2087,7 @@ pub unsafe extern "C-unwind" fn gzputs(file: gzFile, s: *const c_char) -> c_int
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzgetc))]
+#[export_name = crate::prefix!(gzgetc)]
 pub unsafe extern "C-unwind" fn gzgetc(file: gzFile) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
@@ -2119,7 +2131,7 @@ pub unsafe extern "C-unwind" fn gzgetc(file: gzFile) -> c_int {
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzgetc_))]
+#[export_name = crate::prefix!(gzgetc_)]
 pub unsafe extern "C-unwind" fn gzgetc_(file: gzFile) -> c_int {
     // Safety: The caller has ensured that `file` is null or a valid file handle.
     unsafe { gzgetc(file) }
@@ -2143,7 +2155,7 @@ pub unsafe extern "C-unwind" fn gzgetc_(file: gzFile) -> c_int {
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzungetc))]
+#[export_name = crate::prefix!(gzungetc)]
 pub unsafe extern "C-unwind" fn gzungetc(c: c_int, file: gzFile) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
@@ -2252,7 +2264,7 @@ pub unsafe extern "C-unwind" fn gzungetc(c: c_int, file: gzFile) -> c_int {
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
 /// - `buf` must be null or a pointer to at least `len` writable bytes.
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzgets))]
+#[export_name = crate::prefix!(gzgets)]
 pub unsafe extern "C-unwind" fn gzgets(file: gzFile, buf: *mut c_char, len: c_int) -> *mut c_char {
     // Check parameters.
     if buf.is_null() || len < 1 {
@@ -2346,7 +2358,7 @@ pub unsafe extern "C-unwind" fn gzgets(file: gzFile, buf: *mut c_char, len: c_in
 }
 
 /// Dynamically update the compression level and strategy for `file`. See the
-/// description of [`deflateInit2`] for the meaning of these parameters. Previously
+/// description of [`deflateInit2_`] for the meaning of these parameters. Previously
 /// provided data is flushed before applying the parameter changes.
 ///
 /// Note: If `level` is not valid, this function will silently fail with a return
@@ -2363,7 +2375,7 @@ pub unsafe extern "C-unwind" fn gzgets(file: gzFile, buf: *mut c_char, len: c_in
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzsetparams))]
+#[export_name = crate::prefix!(gzsetparams)]
 pub unsafe extern "C-unwind" fn gzsetparams(file: gzFile, level: c_int, strategy: c_int) -> c_int {
     let Ok(strategy) = Strategy::try_from(strategy) else {
         return Z_STREAM_ERROR;
@@ -2433,7 +2445,7 @@ pub unsafe extern "C-unwind" fn gzsetparams(file: gzFile, level: c_int, strategy
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzseek))]
+#[export_name = crate::prefix!(gzseek)]
 pub unsafe extern "C-unwind" fn gzseek(file: gzFile, offset: z_off_t, whence: c_int) -> z_off_t {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
@@ -2540,7 +2552,7 @@ pub unsafe extern "C-unwind" fn gzseek(file: gzFile, offset: z_off_t, whence: c_
 /// # Safety
 ///
 /// - `file`, if non-null, must be an open file handle obtained from [`gzopen`] or [`gzdopen`].
-#[cfg_attr(feature = "export-symbols", export_name = crate::prefix!(gzrewind))]
+#[export_name = crate::prefix!(gzrewind)]
 pub unsafe extern "C-unwind" fn gzrewind(file: gzFile) -> c_int {
     let Some(state) = (unsafe { file.cast::<GzState>().as_mut() }) else {
         return -1;
diff --git a/libz-rs-sys-cdylib/src/lib.rs b/libz-rs-sys-cdylib/src/lib.rs
index 73629974..f74e2e56 100644
--- a/libz-rs-sys-cdylib/src/lib.rs
+++ b/libz-rs-sys-cdylib/src/lib.rs
@@ -2,5 +2,59 @@ extern crate libz_rs_sys;
 
 pub use libz_rs_sys::*;
 
-#[cfg(not(panic = "abort"))]
+#[cfg(not(any(panic = "abort", feature = "__internal-test", test, doc, miri)))]
 compile_error!("panic=\"abort\" is mandatory because unwinding to C is undefined behavior");
+
+#[cfg(feature = "gz")]
+mod gz;
+
+#[cfg(feature = "gz")]
+pub use gz::*;
+
+#[cfg(feature = "gz")]
+#[allow(unused)]
+mod custom_prefix {
+    #[cfg(feature = "custom-prefix")]
+    macro_rules! prefix {
+        ($name:expr) => {
+            concat!(env!("LIBZ_RS_SYS_PREFIX"), stringify!($name))
+        };
+    }
+
+    // NOTE: once we reach 1.0.0, the macro used for the `semver-prefix` feature should no longer include the
+    // minor version in the name. The name is meant to be unique between semver-compatible versions!
+    const _PRE_ONE_DOT_O: () = assert!(env!("CARGO_PKG_VERSION_MAJOR").as_bytes()[0] == b'0');
+
+    #[cfg(feature = "semver-prefix")]
+    macro_rules! prefix {
+        ($name:expr) => {
+            concat!(
+                "LIBZ_RS_SYS_v",
+                env!("CARGO_PKG_VERSION_MAJOR"),
+                "_",
+                env!("CARGO_PKG_VERSION_MINOR"),
+                "_x_",
+                stringify!($name)
+            )
+        };
+    }
+
+    #[cfg(all(not(feature = "custom-prefix"), not(feature = "semver-prefix"),))]
+    macro_rules! prefix {
+        ($name:expr) => {
+            stringify!($name)
+        };
+    }
+
+    #[cfg(all(not(feature = "custom-prefix"), not(feature = "semver-prefix"), test))]
+    macro_rules! prefix {
+        ($name:expr) => {
+            concat!("LIBZ_RS_SYS_TEST_", stringify!($name))
+        };
+    }
+
+    pub(crate) use prefix;
+}
+
+#[cfg(feature = "gz")]
+pub(crate) use custom_prefix::prefix;
diff --git a/libz-rs-sys/src/test-data/example.gz b/libz-rs-sys-cdylib/src/test-data/example.gz
similarity index 100%
rename from libz-rs-sys/src/test-data/example.gz
rename to libz-rs-sys-cdylib/src/test-data/example.gz
diff --git a/libz-rs-sys/src/test-data/example.txt b/libz-rs-sys-cdylib/src/test-data/example.txt
similarity index 100%
rename from libz-rs-sys/src/test-data/example.txt
rename to libz-rs-sys-cdylib/src/test-data/example.txt
diff --git a/libz-rs-sys/src/test-data/incomplete-magic.gz b/libz-rs-sys-cdylib/src/test-data/incomplete-magic.gz
similarity index 100%
rename from libz-rs-sys/src/test-data/incomplete-magic.gz
rename to libz-rs-sys-cdylib/src/test-data/incomplete-magic.gz
diff --git a/libz-rs-sys/src/test-data/magic-only.gz b/libz-rs-sys-cdylib/src/test-data/magic-only.gz
similarity index 100%
rename from libz-rs-sys/src/test-data/magic-only.gz
rename to libz-rs-sys-cdylib/src/test-data/magic-only.gz
diff --git a/libz-rs-sys/Cargo.toml b/libz-rs-sys/Cargo.toml
index 1e5fc6a1..0b14e6d6 100644
--- a/libz-rs-sys/Cargo.toml
+++ b/libz-rs-sys/Cargo.toml
@@ -19,8 +19,6 @@ export-symbols = [] # whether the zlib api symbols are publicly exported
 custom-prefix = ["export-symbols"] # use the LIBZ_RS_SYS_PREFIX to prefix all exported symbols
 testing-prefix = ["export-symbols"] # prefix all symbols with LIBZ_RS_SYS_TEST_ for testing
 semver-prefix = ["export-symbols"] # prefix all symbols in a semver-compatible way
-gz = ["dep:libc"] # gzip support has to be configured explicitly, to avoid a libc dependency in the core zlib-rs
 
 [dependencies]
 zlib-rs = { workspace = true, default-features = false }
-libc = { version = "0.2.171", optional = true }
diff --git a/libz-rs-sys/src/lib.rs b/libz-rs-sys/src/lib.rs
index b46fc359..44ba6f2d 100644
--- a/libz-rs-sys/src/lib.rs
+++ b/libz-rs-sys/src/lib.rs
@@ -37,12 +37,6 @@ use zlib_rs::{
 
 pub use zlib_rs::c_api::*;
 
-#[cfg(feature = "gz")]
-mod gz;
-
-#[cfg(feature = "gz")]
-pub use gz::*;
-
 #[cfg(feature = "custom-prefix")]
 macro_rules! prefix {
     ($name:expr) => {
@@ -60,9 +54,9 @@ macro_rules! prefix {
         concat!(
             "LIBZ_RS_SYS_v",
             env!("CARGO_PKG_VERSION_MAJOR"),
-            ".",
+            "_",
             env!("CARGO_PKG_VERSION_MINOR"),
-            ".x_",
+            "_x_",
             stringify!($name)
         )
     };
diff --git a/test-libz-rs-sys/Cargo.toml b/test-libz-rs-sys/Cargo.toml
index 6a55e566..7ac2f004 100644
--- a/test-libz-rs-sys/Cargo.toml
+++ b/test-libz-rs-sys/Cargo.toml
@@ -13,13 +13,14 @@ rust-version.workspace = true
 
 [features]
 default = ["rust-allocator", "gz"]
-c-allocator = ["libz-rs-sys/c-allocator"]
-rust-allocator = ["libz-rs-sys/rust-allocator"]
-gz = ["libz-rs-sys/gz", "dep:libc"]
+c-allocator = ["libz-rs-sys/c-allocator", "libz-rs-sys-cdylib/c-allocator"]
+rust-allocator = ["libz-rs-sys/rust-allocator", "libz-rs-sys-cdylib/rust-allocator"]
+gz = ["libz-rs-sys-cdylib/gz", "dep:libc"]
 
 [dependencies]
 zlib-rs = { workspace = true, default-features = false, features = ["std", "c-allocator", "rust-allocator", "__internal-test"] }
 libz-rs-sys = { workspace = true, default-features = false, features = ["std", "testing-prefix"] }
+libz-rs-sys-cdylib = { path = "../libz-rs-sys-cdylib", default-features = false, features = ["semver-prefix", "__internal-test"] }
 libz-sys.workspace = true
 libc = { version = "0.2.171", optional = true }
 
diff --git a/test-libz-rs-sys/src/gz.rs b/test-libz-rs-sys/src/gz.rs
index d8f6ad77..a3fc1262 100644
--- a/test-libz-rs-sys/src/gz.rs
+++ b/test-libz-rs-sys/src/gz.rs
@@ -1,6 +1,6 @@
 use zlib_rs::c_api::*;
 
-use libz_rs_sys::{
+use z_rs::{
     gzFile_s, gzbuffer, gzclearerr, gzclose, gzclose_r, gzclose_w, gzdirect, gzdopen, gzerror,
     gzflush, gzfread, gzfwrite, gzgetc, gzgetc_, gzgets, gzoffset, gzopen, gzputc, gzputs, gzread,
     gzrewind, gzseek, gzsetparams, gztell, gzungetc, gzwrite,