CDRIVER-2813 remove BSON_EXTRA_ALIGNMENT option (#1942)

kevinAlbs · eramongodb · web-flow · commit f1e2b54090ea · 2025-03-21T14:15:17.000-04:00
* remove `ENABLE_EXTRA_ALIGNMENT` CMake option
* remove `ENABLE_EXTRA_ALIGNMENT` from test scripts
* remove over-alignment of `bson_t` and `bson_iter_t`
* remove `debug-compile-no-align` task
* remove alignment requirement from `bson_impl_alloc_t`
* add a static assert to ensure that `bson_t` and the implementations have matching alignment.
* remove alignment requirement on `bson_iter_t`
* align `bson_error_t` to size of a pointer
* remove alignment specifier for `bson_value_t`
* remove alignment specifier for `bson_visitor_t`

---------

Co-authored-by: Ezra Chung &lt;88335979+eramongodb@users.noreply.github.com&gt;
diff --git a/.evergreen/config_generator/components/loadbalanced.py b/.evergreen/config_generator/components/loadbalanced.py
@@ -83,7 +83,6 @@ def tasks():
                 env={
                     'CC': _COMPILER,
                     'CFLAGS': '-fno-omit-frame-pointer',
-                    'EXTRA_CONFIGURE_FLAGS': '-DENABLE_EXTRA_ALIGNMENT=OFF',
                     'SSL': 'OPENSSL'
                 },
                 working_dir='mongoc',
diff --git a/.evergreen/config_generator/components/mock_server.py b/.evergreen/config_generator/components/mock_server.py
@@ -42,7 +42,6 @@ def variants():
                 'CC': 'gcc',
                 'ASAN': 'on',
                 'CFLAGS': '-fno-omit-frame-pointer',
-                'EXTRA_CONFIGURE_FLAGS': '-DENABLE_EXTRA_ALIGNMENT=OFF',
                 'SANITIZE': 'address,undefined',
             }
         ),
diff --git a/.evergreen/config_generator/components/sanitizers/asan.py b/.evergreen/config_generator/components/sanitizers/asan.py
@@ -10,7 +10,6 @@ def variants():
         'ASAN': 'on',
         'CFLAGS': '-fno-omit-frame-pointer',
         'CHECK_LOG': 'ON',
-        'EXTRA_CONFIGURE_FLAGS': '-DENABLE_EXTRA_ALIGNMENT=OFF',
         'SANITIZE': 'address,undefined',
     }
 
diff --git a/.evergreen/config_generator/components/sanitizers/tsan.py b/.evergreen/config_generator/components/sanitizers/tsan.py
@@ -9,7 +9,7 @@ def variants():
     expansions = {
         'CFLAGS': '-fno-omit-frame-pointer',
         'CHECK_LOG': 'ON',
-        'EXTRA_CONFIGURE_FLAGS': '-DENABLE_EXTRA_ALIGNMENT=OFF -DENABLE_SHM_COUNTERS=OFF',
+        'EXTRA_CONFIGURE_FLAGS': '-DENABLE_SHM_COUNTERS=OFF',
         'SANITIZE': 'thread',
     }
 
diff --git a/.evergreen/generated_configs/legacy-config.yml b/.evergreen/generated_configs/legacy-config.yml
@@ -355,21 +355,6 @@ tasks:
         set -o errexit
         env SNAPPY="OFF" ZLIB="OFF" ZSTD="ON" .evergreen/scripts/compile.sh
   - func: upload-build
-- name: debug-compile-no-align
-  tags:
-  - debug-compile
-  commands:
-  - func: find-cmake-latest
-  - command: shell.exec
-    type: test
-    params:
-      working_dir: mongoc
-      add_expansions_to_env: true
-      shell: bash
-      script: |-
-        set -o errexit
-        env EXTRA_CONFIGURE_FLAGS="-DENABLE_EXTRA_ALIGNMENT=OFF" SNAPPY="OFF" ZLIB="BUNDLED" ZSTD="OFF" .evergreen/scripts/compile.sh
-  - func: upload-build
 - name: debug-compile-nosasl-nossl
   tags:
   - debug-compile
@@ -1311,7 +1296,7 @@ tasks:
       shell: bash
       script: |-
         set -o errexit
-        env SANITIZE=address SASL=AUTO SSL=OPENSSL EXTRA_CONFIGURE_FLAGS='-DENABLE_EXTRA_ALIGNMENT=OFF' .evergreen/scripts/compile.sh
+        env SANITIZE=address SASL=AUTO SSL=OPENSSL .evergreen/scripts/compile.sh
   - func: prepare-kerberos
   - func: run auth tests
     vars:
@@ -16373,7 +16358,6 @@ buildvariants:
   tasks:
   - release-compile
   - debug-compile-nosasl-nossl
-  - debug-compile-no-align
   - .debug-compile !.sspi .nossl .nosasl
   - .latest .nossl .nosasl
 - name: gcc82rhel
@@ -16417,7 +16401,6 @@ buildvariants:
   tasks:
   - release-compile
   - debug-compile-nosasl-nossl
-  - debug-compile-no-align
   - .latest .nossl .nosasl
 - name: gcc94
   display_name: GCC 9.4 (Ubuntu 20.04)
@@ -16429,7 +16412,6 @@ buildvariants:
   - debug-compile-nosrv
   - release-compile
   - debug-compile-nosasl-nossl
-  - debug-compile-no-align
   - debug-compile-sasl-openssl
   - debug-compile-nosasl-openssl
   - .authentication-tests .openssl
@@ -16449,7 +16431,6 @@ buildvariants:
   - .compression !.snappy
   - release-compile
   - debug-compile-nosasl-nossl
-  - debug-compile-no-align
   - debug-compile-nosrv
   - debug-compile-sasl-darwinssl
   - debug-compile-nosasl-nossl
@@ -16507,13 +16488,6 @@ buildvariants:
   tasks:
   - debug-compile-nosasl-nossl
   - .latest .nossl .nosasl .server
-- name: mingw
-  display_name: MinGW-W64
-  expansions:
-    CC: mingw
-  run_on: windows-vsCurrent-large
-  tasks:
-  - debug-compile-no-align
 - name: rhel8-power
   display_name: Power (ppc64le) (RHEL 8)
   expansions:
@@ -16534,7 +16508,6 @@ buildvariants:
   run_on: ubuntu2004-arm64-large
   tasks:
   - .compression !.snappy !.zstd
-  - debug-compile-no-align
   - release-compile
   - debug-compile-nosasl-nossl
   - debug-compile-nosasl-openssl
@@ -16550,7 +16523,6 @@ buildvariants:
   run_on: rhel8-zseries-large
   tasks:
   - release-compile
-  - debug-compile-no-align
   - debug-compile-nosasl-nossl
   - debug-compile-nosasl-openssl
   - debug-compile-sasl-openssl
diff --git a/.evergreen/generated_configs/tasks.yml b/.evergreen/generated_configs/tasks.yml
@@ -2949,7 +2949,6 @@ tasks:
           env:
             CC: gcc
             CFLAGS: -fno-omit-frame-pointer
-            EXTRA_CONFIGURE_FLAGS: -DENABLE_EXTRA_ALIGNMENT=OFF
             SSL: OPENSSL
           args:
             - -c
diff --git a/.evergreen/generated_configs/variants.yml b/.evergreen/generated_configs/variants.yml
@@ -180,7 +180,6 @@ buildvariants:
       ASAN: "on"
       CC: gcc
       CFLAGS: -fno-omit-frame-pointer
-      EXTRA_CONFIGURE_FLAGS: -DENABLE_EXTRA_ALIGNMENT=OFF
       SANITIZE: address,undefined
     tasks:
       - name: mock-server-test
@@ -194,7 +193,6 @@ buildvariants:
       ASAN: "on"
       CFLAGS: -fno-omit-frame-pointer
       CHECK_LOG: "ON"
-      EXTRA_CONFIGURE_FLAGS: -DENABLE_EXTRA_ALIGNMENT=OFF
       SANITIZE: address,undefined
     tasks:
       - name: .sanitizers-matrix-asan
@@ -203,7 +201,7 @@ buildvariants:
     expansions:
       CFLAGS: -fno-omit-frame-pointer
       CHECK_LOG: "ON"
-      EXTRA_CONFIGURE_FLAGS: -DENABLE_EXTRA_ALIGNMENT=OFF -DENABLE_SHM_COUNTERS=OFF
+      EXTRA_CONFIGURE_FLAGS: -DENABLE_SHM_COUNTERS=OFF
       SANITIZE: thread
     tasks:
       - name: .sanitizers-matrix-tsan
diff --git a/.evergreen/legacy_config_generator/evergreen_config_lib/tasks.py b/.evergreen/legacy_config_generator/evergreen_config_lib/tasks.py
@@ -151,7 +151,6 @@ class CompileWithClientSideEncryptionAsan(CompileTask):
         CFLAGS="-fno-omit-frame-pointer",
         COMPILE_LIBMONGOCRYPT="ON",
         CHECK_LOG="ON",
-        EXTRA_CONFIGURE_FLAGS="-DENABLE_EXTRA_ALIGNMENT=OFF",
         PATH="/usr/lib/llvm-3.8/bin:$PATH",
     )
     cls_tags: ClassVar[Sequence[str]] = ["client-side-encryption"]
@@ -187,12 +186,6 @@ def __init__(
     CompileTask("debug-compile-compression-zlib", tags=["zlib", "compression"], compression="zlib"),
     CompileTask("debug-compile-compression-snappy", tags=["snappy", "compression"], compression="snappy"),
     CompileTask("debug-compile-compression-zstd", tags=["zstd", "compression"], compression="zstd"),
-    CompileTask(
-        "debug-compile-no-align",
-        tags=["debug-compile"],
-        compression="zlib",
-        EXTRA_CONFIGURE_FLAGS="-DENABLE_EXTRA_ALIGNMENT=OFF",
-    ),
     CompileTask("debug-compile-nosasl-nossl", tags=["debug-compile", "nosasl", "nossl"], SSL="OFF"),
     CompileTask("debug-compile-lto", CFLAGS="-flto"),
     CompileTask("debug-compile-lto-thin", CFLAGS="-flto=thin"),
@@ -697,7 +690,7 @@ def pre_commands(self) -> Iterable[Value]:
                 func("find-cmake-latest"),
                 shell_mongoc(
                     """
-            env SANITIZE=address SASL=AUTO SSL=OPENSSL EXTRA_CONFIGURE_FLAGS='-DENABLE_EXTRA_ALIGNMENT=OFF' .evergreen/scripts/compile.sh
+            env SANITIZE=address SASL=AUTO SSL=OPENSSL .evergreen/scripts/compile.sh
             """,
                     add_expansions_to_env=True,
                 ),
diff --git a/.evergreen/legacy_config_generator/evergreen_config_lib/variants.py b/.evergreen/legacy_config_generator/evergreen_config_lib/variants.py
@@ -111,7 +111,6 @@ def days(n: int) -> int:
         [
             "release-compile",
             "debug-compile-nosasl-nossl",
-            "debug-compile-no-align",
             ".debug-compile !.sspi .nossl .nosasl",
             ".latest .nossl .nosasl",
         ],
@@ -151,7 +150,7 @@ def days(n: int) -> int:
         "gcc94-i686",
         "GCC 9.4 (i686) (Ubuntu 20.04)",
         "ubuntu2004-test",
-        ["release-compile", "debug-compile-nosasl-nossl", "debug-compile-no-align", ".latest .nossl .nosasl"],
+        ["release-compile", "debug-compile-nosasl-nossl", ".latest .nossl .nosasl"],
         {"CC": "gcc", "MARCH": "i686"},
     ),
     Variant(
@@ -163,7 +162,6 @@ def days(n: int) -> int:
             "debug-compile-nosrv",
             "release-compile",
             "debug-compile-nosasl-nossl",
-            "debug-compile-no-align",
             "debug-compile-sasl-openssl",
             "debug-compile-nosasl-openssl",
             ".authentication-tests .openssl",
@@ -185,7 +183,6 @@ def days(n: int) -> int:
             ".compression !.snappy",
             "release-compile",
             "debug-compile-nosasl-nossl",
-            "debug-compile-no-align",
             "debug-compile-nosrv",
             "debug-compile-sasl-darwinssl",
             "debug-compile-nosasl-nossl",
@@ -250,7 +247,6 @@ def days(n: int) -> int:
         ["debug-compile-nosasl-nossl", ".latest .nossl .nosasl .server"],
         {"CC": "mingw"},
     ),
-    Variant("mingw", "MinGW-W64", "windows-vsCurrent-large", ["debug-compile-no-align"], {"CC": "mingw"}),
     Variant(
         "rhel8-power",
         "Power (ppc64le) (RHEL 8)",
@@ -272,7 +268,6 @@ def days(n: int) -> int:
         "ubuntu2004-arm64-large",
         [
             ".compression !.snappy !.zstd",
-            "debug-compile-no-align",
             "release-compile",
             "debug-compile-nosasl-nossl",
             "debug-compile-nosasl-openssl",
@@ -291,7 +286,6 @@ def days(n: int) -> int:
         [
             "release-compile",
             #      '.compression', --> TODO: waiting on ticket CDRIVER-3258
-            "debug-compile-no-align",
             "debug-compile-nosasl-nossl",
             "debug-compile-nosasl-openssl",
             "debug-compile-sasl-openssl",
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -185,19 +185,6 @@ mongo_bool_setting(
    ]]
 )
 
-# Deprecated options:
-mongo_bool_setting(
-   ENABLE_EXTRA_ALIGNMENT
-      "[Deprecated] Enable extra alignment on libbson types"
-   DEFAULT VALUE ON
-      DEVEL VALUE OFF
-   VALIDATE CODE [[
-      if(ENABLE_EXTRA_ALIGNMENT AND MONGO_SANITIZE MATCHES "undefined")
-         message(WARNING "ENABLE_EXTRA_ALIGNMENT=“${ENABLE_EXTRA_ALIGNMENT}” will create conflicts with UndefinedBehaviorSanitizer")
-      endif()
-   ]]
-)
-
 # Announce the build configuration. Used by `mlib_build_config_is()` in `mlib/config.h`
 add_compile_definitions(_MLIB_BUILD_CONFIG=$<CONFIG>)
 
@@ -302,8 +289,6 @@ if ( (ENABLE_BUILD_DEPENDECIES STREQUAL OFF) AND (NOT CMAKE_CURRENT_SOURCE_DIR S
    set (ENABLE_BUILD_DEPENDECIES ON)
 endif ()
 
-mongo_pick(BSON_EXTRA_ALIGN 1 0 ENABLE_EXTRA_ALIGNMENT)
-
 mongo_pick(MONGOC_ENABLE_RDTSCP 1 0 ENABLE_RDTSCP)
 
 mongo_pick(MONGOC_ENABLE_STATIC_BUILD 1 0 ENABLE_STATIC)
diff --git a/Earthfile b/Earthfile
@@ -39,7 +39,6 @@ build:
     RUN cmake -S "$source_dir" -B "$build_dir" -G "Ninja Multi-Config" \
         -D ENABLE_MAINTAINER_FLAGS=ON \
         -D ENABLE_SHM_COUNTERS=ON \
-        -D ENABLE_EXTRA_ALIGNMENT=OFF \
         -D ENABLE_SASL=$(echo $sasl | __str upper) \
         -D ENABLE_SNAPPY=ON \
         -D ENABLE_SRV=ON \
diff --git a/src/libbson/NEWS b/src/libbson/NEWS
@@ -12,6 +12,11 @@ libbson 2.0.0 (Unreleased)
 * Compiling with `BSON_MEMCHECK` defined now has no effect.
 * Remove deprecated integral comparison interfaces: `bson_in_range_*` and `bson_cmp_*`.
 * Remove deprecated atomic and threading interfaces: `bson_atomic_*` and `bson_thrd_yield`.
+* The deprecated `ENABLE_EXTRA_ALIGNMENT` CMake option is removed.
+  * `bson_t` and `bson_iter_t` are now aligned to the size of a pointer instead of `128`.
+  * `bson_error_t`, `bson_value_t`, and `bson_visitor_t` are now aligned to the size of a pointer instead of `8`.
+  * `BSON_ALIGNED_BEGIN` and `BSON_ALIGNED_END` now unconditionally apply their requested alignment.
+
 
 libbson 1.30.2
 ==============
diff --git a/src/libbson/doc/bson_t.rst b/src/libbson/doc/bson_t.rst
@@ -127,12 +127,11 @@ Synopsis
   #define BSON_APPEND_VALUE(b, key, val) \
      bson_append_value (b, key, (int) strlen (key), (val))
 
-  BSON_ALIGNED_BEGIN (128)
   typedef struct {
      uint32_t flags;       /* Internal flags for the bson_t. */
      uint32_t len;         /* Length of BSON data. */
      uint8_t padding[120]; /* Padding for stack allocation. */
-  } bson_t BSON_ALIGNED_END (128);
+  } bson_t;
 
 Description
 -----------
diff --git a/src/libbson/src/bson/bson-config.h.in b/src/libbson/src/bson/bson-config.h.in
@@ -96,14 +96,6 @@
 #endif
 
 
-/*
- * Define to 1 if you want extra aligned types in libbson
- */
-#define BSON_EXTRA_ALIGN @BSON_EXTRA_ALIGN@
-#if BSON_EXTRA_ALIGN != 1
-# undef BSON_EXTRA_ALIGN
-#endif
-
 
 /*
  * Define to 1 if you have rand_r available on your platform.
diff --git a/src/libbson/src/bson/bson-macros.h b/src/libbson/src/bson/bson-macros.h
@@ -162,23 +162,13 @@
 #define BSON_ALIGN_OF_PTR (BSON_ALIGNOF (void *))
 #endif
 
-#ifdef BSON_EXTRA_ALIGN
-#if defined(_MSC_VER)
-#define BSON_ALIGNED_BEGIN(_N) __declspec (align (_N))
-#define BSON_ALIGNED_END(_N)
-#else
-#define BSON_ALIGNED_BEGIN(_N)
-#define BSON_ALIGNED_END(_N) __attribute__ ((aligned (_N)))
-#endif
-#else
 #if defined(_MSC_VER)
 #define BSON_ALIGNED_BEGIN(_N) __declspec (align (BSON_ALIGN_OF_PTR))
 #define BSON_ALIGNED_END(_N)
 #else
 #define BSON_ALIGNED_BEGIN(_N)
 #define BSON_ALIGNED_END(_N) __attribute__ ((aligned ((_N) > BSON_ALIGN_OF_PTR ? BSON_ALIGN_OF_PTR : (_N))))
 #endif
-#endif
 
 
 #define bson_str_empty(s) (!s[0])
diff --git a/src/libbson/src/bson/bson-private.h b/src/libbson/src/bson/bson-private.h
@@ -43,18 +43,16 @@ typedef enum {
 #define BSON_INLINE_DATA_SIZE 120
 
 
-BSON_ALIGNED_BEGIN (128)
+BSON_ALIGNED_BEGIN (BSON_ALIGN_OF_PTR)
 typedef struct {
    bson_flags_t flags;
    uint32_t len;
    uint8_t data[BSON_INLINE_DATA_SIZE];
-} bson_impl_inline_t BSON_ALIGNED_END (128);
+} bson_impl_inline_t BSON_ALIGNED_END (BSON_ALIGN_OF_PTR);
 
 
 BSON_STATIC_ASSERT2 (impl_inline_t, sizeof (bson_impl_inline_t) == 128);
 
-
-BSON_ALIGNED_BEGIN (128)
 typedef struct {
    bson_flags_t flags; /* flags describing the bson_t */
    /* len is part of the public bson_t declaration. It is not
@@ -71,11 +69,16 @@ typedef struct {
    size_t alloclen;           /* length of buffer that we own. */
    bson_realloc_func realloc; /* our realloc implementation */
    void *realloc_func_ctx;    /* context for our realloc func */
-} bson_impl_alloc_t BSON_ALIGNED_END (128);
+} bson_impl_alloc_t;
 
 
 BSON_STATIC_ASSERT2 (impl_alloc_t, sizeof (bson_impl_alloc_t) <= 128);
 
+// Ensure both `bson_t` implementations have the same alignment requirement:
+BSON_STATIC_ASSERT2 (impls_match_alignment, BSON_ALIGNOF (bson_impl_inline_t) == BSON_ALIGNOF (bson_impl_alloc_t));
+// Ensure `bson_t` has same alignment requirement as implementations:
+BSON_STATIC_ASSERT2 (impls_match_alignment, BSON_ALIGNOF (bson_t) == BSON_ALIGNOF (bson_impl_alloc_t));
+
 
 BSON_END_DECLS
 
diff --git a/src/libbson/src/bson/bson-types.h b/src/libbson/src/bson/bson-types.h

Original file line number	Diff line number	Diff line change
`@@ -42,7 +42,6 @@ def variants():`
`42`	`42`	`'CC': 'gcc',`
`43`	`43`	`'ASAN': 'on',`
`44`	`44`	`'CFLAGS': '-fno-omit-frame-pointer',`
`45`		`- 'EXTRA_CONFIGURE_FLAGS': '-DENABLE_EXTRA_ALIGNMENT=OFF',`
`46`	`45`	`'SANITIZE': 'address,undefined',`
`47`	`46`	`}`
`48`	`47`	`),`
Original file line number	Diff line number	Diff line change
`@@ -10,7 +10,6 @@ def variants():`
`10`	`10`	`'ASAN': 'on',`
`11`	`11`	`'CFLAGS': '-fno-omit-frame-pointer',`
`12`	`12`	`'CHECK_LOG': 'ON',`
`13`		`- 'EXTRA_CONFIGURE_FLAGS': '-DENABLE_EXTRA_ALIGNMENT=OFF',`
`14`	`13`	`'SANITIZE': 'address,undefined',`
`15`	`14`	`}`
`16`	`15`
Original file line number	Diff line number	Diff line change
`@@ -9,7 +9,7 @@ def variants():`
`9`	`9`	`expansions = {`
`10`	`10`	`'CFLAGS': '-fno-omit-frame-pointer',`
`11`	`11`	`'CHECK_LOG': 'ON',`
`12`		`- 'EXTRA_CONFIGURE_FLAGS': '-DENABLE_EXTRA_ALIGNMENT=OFF -DENABLE_SHM_COUNTERS=OFF',`
	`12`	`+ 'EXTRA_CONFIGURE_FLAGS': '-DENABLE_SHM_COUNTERS=OFF',`
`13`	`13`	`'SANITIZE': 'thread',`
`14`	`14`	`}`
`15`	`15`