feat(pkgs): add compat.spdlog 1.17.0 (header-only + declarative compi… (#72)

1115040131 · d2learn-org · web-flow · commit af923e519af4 · 2026-07-16T00:00:59.000+08:00
* feat(pkgs): add compat.spdlog 1.17.0 (header-only + declarative compiled feature)

spdlog is dual-modal: default header-only (self-contained via bundled fmt in
FMT_HEADER_ONLY mode, no external fmt dep) and a precompiled mode gated on
SPDLOG_COMPILED_LIB. The `compiled` feature declares the correct intent
(sources = src/*.cpp + the SPDLOG_COMPILED_LIB interface define), but mcpp
0.0.91 does not yet compile a dependency's feature-gated sources — verified
three ways (this package, compat.cjson's utils, compat.eigen's eigen_blas all
leave feature sources uncompiled → link-time undefined reference). The feature's
`defines` DO propagate to the consumer. So CI asserts the fully-working
header-only mode; the compiled feature works unchanged once the engine links
feature sources (same follow-up as eigen_blas).

No CN mirror (no mcpp-res write access): plain-string upstream url per the
docs/cn-mirror.md fallback (tensorvia-cpu precedent).

Verified on mcpp 0.0.91 (GLOBAL): xpkg parse OK, `mcpp test -p spdlog` passes.

* fix(spdlog): 修正引擎限制误判 + compiled 模态进 CI(mcpp 0.0.94)

初版把「feature sources 不编译」判为引擎级限制,是**误判**:该 bug 只影响
`mcpp test` 路径,`mcpp build` 一直是好的(7 个 src TU 全进 build.ninja、
二进制真跑)。三重佐证(spdlog/cjson/eigen)现象属实,但三次都只走了 test
一条路径 —— 本仓 CI 是 workspace/test 模型。

真因(mcpp/src/build/prepare.cppm):feature 源集解析被整段门在
`!includeDevDeps`,test 模式跳过 → 激活 feature 的 sources 从不加回构建图;
叠加 xpkg 的 `features.X.sources` 只落进 featureSources、从不进 base sources。
已由 mcpp#218 修复并发布 0.0.94(drop 仍只在 build 模式,add 两模式都做+去重)。

- 描述符 Lua **一行未改** —— `compiled` feature 的建模本来就是对的;
  只把注释从「引擎不支持、请用 header-only」改为如实的「test 下需 ≥0.0.94」。
- 新增 workspace 成员 `tests/examples/spdlog-compiled/`:**compiled 模态进 CI**。
  静态断言 SPDLOG_COMPILED_LIB 已定义 + SPDLOG_HEADER_ONLY 未定义(退化回
  inline 路径是编译错误而非静默通过),再跑行为断言 —— 调用解析到
  default_logger_raw / log_msg ctor / logger::log_it_ / bundled fmt vformat
  等非 inline 符号,正是 feature sources 没编译时链不上的那批。
- CI pin 0.0.91 → 0.0.94;index floor `min_mcpp` 不动(它追踪描述符**语法**,
  本描述符在 0.0.87 上就能解析;header-only 模态任何版本都可用)。
- 修 `tests/examples/spdlog/mcpp.toml` 里 `pkgs/s/` 陈旧路径 → `pkgs/c/`。

---------

Co-authored-by: sunrisepeak &lt;x.d2learn.org@gmail.com&gt;
diff --git a/.agents/docs/2026-07-15-add-spdlog-plan.md b/.agents/docs/2026-07-15-add-spdlog-plan.md
@@ -0,0 +1,154 @@
+# 收录 spdlog 1.17.0 —— 形态判定、双模态与验证结论
+
+日期:2026-07-15。对应描述符 `pkgs/c/compat.spdlog.lua`、示例 `tests/examples/spdlog/`。
+CI 版本 mcpp 0.0.91,index floor `min_mcpp = 0.0.87`。
+
+## 1. 来源与形态
+
+- 来源:(a) 第三方上游库 —— spdlog(https://github.com/gabime/spdlog)上游不提供
+  mcpp 支持,由本仓以 `compat` 形态适配。
+- 最新 tag:`v1.17.0`(`git ls-remote --tags` 排序确认)。裸版本 `1.17.0`,
+  下载 URL 保留上游 `.../v1.17.0.tar.gz` 拼写。
+- License:MIT。
+- sha256:`d8862955c6d74e5846b3f580b1605d2428b11d97a410d86e2fb13e857cd3a744`
+  (下载后重复计算两次,稳定)。
+- 源码布局:`include/spdlog/**`(全部头文件,含 `-inl.h` 实现单元与
+  `fmt/bundled/` 内联版 {fmt})、`src/*.cpp`(7 个预编译库 TU)。
+- 形态判定:**header-only + source-gated feature**,与 `compat.eigen` 同类。
+  spdlog 是 DUAL-MODAL:
+  - 默认(不定义宏)走 header-only:`common.h` 在未定义 `SPDLOG_COMPILED_LIB`
+    时打开 `SPDLOG_HEADER_ONLY`,头文件末尾 `#include "*-inl.h"` 把实现内联。
+    bundled fmt 以 `FMT_HEADER_ONLY` 使用,**整包自包含,无需外部 fmt 依赖**。
+  - 预编译模态(定义 `SPDLOG_COMPILED_LIB`)改为编译 `src/*.cpp`;每个 src TU
+    在缺少该宏时 `#error`。该宏是 **interface define**:必须同时到达库源与
+    消费者头(否则消费者头走 inline,与 .a 符号重复/冲突)。
+
+## 2. 描述符设计
+
+header-only 骨架(`include_dirs = {"*/include"}` + anchor TU 提供可构建 lib
+target),外加一个声明式 `compiled` feature:
+
+```lua
+features = {
+    ["compiled"] = {
+        sources = { "*/src/*.cpp" },
+        defines = { "SPDLOG_COMPILED_LIB" },
+    },
+}
+```
+
+## 3. 关键实证:feature sources 在 `mcpp test` 下不编译(mcpp ≤0.0.93 的 bug,0.0.94 已修)
+
+> **修订(2026-07-15)**:本节初版结论「mcpp 0.0.91 引擎不编译 feature 门控的
+> sources」**是误判**,已由 mcpp#218 查清并修复。误判的成因值得记下来。
+
+初版三重佐证如下:
+
+| 实验 | feature | 现象 |
+|---|---|---|
+| spdlog | `compiled` | `src/*.cpp` 未编译 → 大量 `undefined reference` |
+| compat.cjson | `utils` | `cJSON_Utils.c` 未编译 → `undefined reference to cJSONUtils_*` |
+| compat.eigen | `eigen_blas` | `blas/*.cpp` 未编译 → `undefined reference to dgemm_` |
+
+三例现象属实,但**三次都只走了 `mcpp test` 这一条路径**(本仓 CI 是 workspace/test
+模型),于是把一个**只影响 test 模式**的 bug 误读成了「引擎不支持 feature sources」。
+
+**真因**(`mcpp/src/build/prepare.cppm`):feature 源集解析(drop + add)**整段**被门在
+`!includeDevDeps`,而 `mcpp test` 走 `includeDevDeps = true` → 激活 feature 的 sources
+从不被加回构建图。叠加 xpkg 侧 `features.X.sources` 只落进 `featureSources`、**从不进
+base `sources`** —— 于是「只在 features 下声明」的包:
+
+| 路径 | 结果 |
+|---|---|
+| `mcpp build` | ✅ **一直是好的**,7 个 src TU 全进 build.ninja,二进制真跑 |
+| `mcpp test` | ❌ `undefined reference` |
+
+那段门的注释假设「descriptor 会把 `gtest_main.cc` 同时留在 base sources 里,故 test
+模式不受影响」——**只对 gtest 成立**,是未被察觉的隐式耦合。`compat.eigen` 里
+"linking feature-built dependency objects into test binaries is a follow-up" 的定性
+同样是错的:**不是链接问题,是源集解析问题**。
+
+**修复**:mcpp 0.0.94(#218)—— drop 仍只在 build 模式做(test 模式需保留完整源面供
+dev-dep 轨 per-test main 检测剪枝),add 改为两模式都做 + 去重。
+
+**采用方案**:描述符的 `compiled` feature 声明**本来就是对的,一行未改**;只把注释从
+「引擎不支持」改为如实的「`mcpp test` 下需 ≥0.0.94」。CI pin 提到 0.0.94 后,
+**两个模态都进 CI 断言**(`tests/examples/spdlog/` header-only +
+`tests/examples/spdlog-compiled/` compiled)。
+
+**教训**:诊断 feature 相关问题**必须 `build` / `test` 两条路径对比**,只测一条会把
+路径 bug 误判成引擎能力缺失。
+
+## 4. feature 评估:为何不为 tweakme 开关新增 feature
+
+spdlog 的 `tweakme.h` 有大量编译期开关(`SPDLOG_USE_STD_FORMAT`、
+`SPDLOG_NO_SOURCE_LOC`、`SPDLOG_CLOCK_COARSE`、`SPDLOG_ACTIVE_LEVEL=...` 等)。
+经确认(mcpp `05-mcpp-toml.md`),消费者可在**自己的** `mcpp.toml` 直接注入,
+无需包侧声明 feature:
+
+```toml
+[targets.my-app]
+defines  = ["SPDLOG_USE_STD_FORMAT"]   # per-target,-D 随本 TU 编译
+# 或 [build] cxxflags = ["-DSPDLOG_NO_SOURCE_LOC"]  # 整工程
+```
+
+作用域陷阱(官方明示):`defines`/`cxxflags` **只作用于该 target 自己的 entry,
+不传播到共享/依赖代码**。对 spdlog:
+
+- header-only 模态下 spdlog 全在头文件里,随消费者 TU 编译,消费者 `-D` 天然覆盖
+  → 所有 tweakme 开关消费者自助即可,做成 feature 是冗余(且不如消费侧灵活,
+  消费侧还能带值,如 `SPDLOG_ACTIVE_LEVEL=SPDLOG_LEVEL_INFO`)。
+- 唯一"消费者 `-D` 够不着、必须包侧统一注入"的是 `SPDLOG_COMPILED_LIB`
+  (要同时影响库源与消费者)——已由 `compiled` feature 承载(受 §3 限制)。
+
+因此**不新增 tweakme feature**,避免过度设计。
+
+## 5. CN 镜像:纯字符串回退
+
+本环境无 gitcode token(`~/.config/gitcode-tool/config.json` 不存在,
+`GITCODE_TOKEN` 未设),无法在 `mcpp-res` 上传资产。探查发现 `mcpp-res/spdlog`
+仓库页面已存在(200)但为空壳(release 资产 403)。
+
+按 `docs/cn-mirror.md` 回退方案:三平台 `url` 采用**纯字符串**(仅上游 GitHub
+release),lint(`check_mirror_urls.lua`)对纯字符串 url 不施加镜像约束,
+`mirror-cn-reachable` 也不会抽取到需 curl 的 CN url。CN 用户回退至上游源。
+先例:`pkgs/t/tensorvia-cpu.lua`。后续获得权限或维护者补充镜像后,可将各
+`url` 改写为 `{ GLOBAL, CN }` 表(sha256 不变)。
+
+lint 只允许 `gitcode.com/mcpp-res/` 下的 CN url(信任边界 + 字节一致),任何
+第三方域名在表形式下都过不了 lint,故无"其他可用 CN 镜像"。
+
+## 6. 验证结论(mcpp 0.0.94,GLOBAL)
+
+**两个模态都已 CI 断言**:
+
+- `mcpp test -p spdlog` → header-only 默认模态,`test result ok. 1 passed`。
+- `mcpp test -p spdlog-compiled` → compiled 模态,`test result ok. 1 passed`。
+  `tests/examples/spdlog-compiled/tests/compiled_test.cpp` 静态断言
+  `SPDLOG_COMPILED_LIB` 已定义且 `SPDLOG_HEADER_ONLY` 未定义(退化回 inline 路径
+  会是**编译错误**而非静默通过),再跑与 header-only 同款的行为断言 —— 这些调用
+  解析到 `default_logger_raw` / `log_msg` ctor / `logger::log_it_` / bundled fmt
+  `vformat` 等**非 inline 符号**,正是 feature sources 没编译时链不上的那批。
+
+以下为初版(0.0.91)记录,保留作历史:
+
+- `mcpp xpkg parse pkgs/c/compat.spdlog.lua` → `parse OK`(strict floor/grammar)。
+- workspace 成员 `mcpp test -p spdlog` → `test result ok. 1 passed`。
+  示例 `tests/examples/spdlog/tests/log_test.cpp` 用 ostream sink 捕获日志,
+  断言 `logger.info("hello {}={}", "answer", 42)` 与 `{:#x}` 的格式化输出
+  (走 bundled fmt 头内联),`return ok ? 0 : 1`。
+- 负向语义:header-only 默认构建 `build.ninja` 仅 `spdlog_anchor.o`
+  (证明 src 未被默认编入);compiled 请求时消费者带 `-DSPDLOG_COMPILED_LIB`
+  (证明 define 门控生效)。
+- 本地 lint(等价 CI lint job)全量 `ALL LINT PASS`;spdlog 镜像 lint 单独 OK。
+
+## 7. 落点与注意事项
+
+- 描述符落点 `pkgs/c/compat.spdlog.lua`——目录取**完整包名首字母**
+  (`compat.spdlog` → `c`,非短名 `s`)。初次误置 `pkgs/s/` 导致
+  `not found in local index`,移至 `pkgs/c/` 后解决。
+- 示例已登记进根 `mcpp.toml` 的 `[workspace].members`(否则
+  `mcpp test --workspace` 不会跑到)。
+- CI 已由早期 `detect`+`run_example.sh` 重构为 workspace 模式
+  (`mcpp test --workspace`),示例采用 `tests/*.cpp` + 断言布局,而非
+  `src/main.cpp`。
diff --git a/.github/workflows/validate.yml b/.github/workflows/validate.yml
@@ -11,11 +11,12 @@ on:
   workflow_dispatch:
 
 env:
-  # Bumped to 0.0.91: carries standard = "c++fly" (experimental playground
-  # mode) in the resolver grammar — required so descriptors declaring it get
-  # the lint WARN below instead of a hard grammar-parse rejection from an
-  # older pinned mcpp (admission policy: warn, don't reject).
-  MCPP_VERSION: "0.0.91"
+  # Bumped to 0.0.94: fixes feature-gated `sources` never being compiled under
+  # `mcpp test` (mcpp#218) — required by the tests/examples/spdlog-compiled
+  # member, which links against spdlog's feature-compiled src/*.cpp. Also
+  # carries standard = "c++fly" in the resolver grammar (0.0.91), so c++fly
+  # descriptors get the lint WARN below, not a hard grammar-parse rejection.
+  MCPP_VERSION: "0.0.94"
 
 jobs:
   lint:
diff --git a/mcpp.toml b/mcpp.toml
@@ -20,4 +20,6 @@ members = [
     "tests/examples/nlohmann.json",
     "tests/examples/openblas",
     "tests/examples/opencv",
+    "tests/examples/spdlog",
+    "tests/examples/spdlog-compiled",
 ]
diff --git a/pkgs/c/compat.spdlog.lua b/pkgs/c/compat.spdlog.lua
@@ -0,0 +1,103 @@
+-- Form B inline descriptor for spdlog — a very fast, header-only / compiled C++
+-- logging library. spdlog is DUAL-MODAL and this recipe exposes both modes off
+-- one descriptor:
+--
+--   * DEFAULT (header-only). No feature requested. spdlog's headers are
+--     self-contained: including <spdlog/spdlog.h> pulls the -inl.h
+--     implementation inline (common.h flips on SPDLOG_HEADER_ONLY when
+--     SPDLOG_COMPILED_LIB is NOT defined). Nothing under src/ compiles; a tiny
+--     anchor TU gives mcpp a buildable `lib` target (same shape as
+--     compat.eigen / compat.opengl). The bundled {fmt} (include/spdlog/fmt/
+--     bundled/) is used in FMT_HEADER_ONLY mode, so this package is
+--     self-contained and needs NO external fmt dependency.
+--
+--   * COMPILED (`features = ["compiled"]`). Turns spdlog into a precompiled
+--     library: (1) compiles the seven src/*.cpp translation units into the lib,
+--     and (2) contributes the SPDLOG_COMPILED_LIB define. That define is an
+--     INTERFACE define — it must reach BOTH spdlog's own sources (each src/*.cpp
+--     #errors out without it) AND every consumer TU that includes a spdlog
+--     header (so the consumer's headers switch to the extern-template /
+--     non-inline path and link against the compiled objects instead of
+--     re-emitting the implementation inline). bundled_fmtlib_format.cpp compiles
+--     the bundled fmt implementation into the lib, so compiled mode is
+--     self-contained too — still NO external fmt dependency.
+--
+--     REQUIRES mcpp >= 0.0.94 under `mcpp test`. mcpp 0.0.93 and older gated the
+--     whole feature-source resolution on build mode, so an active feature's
+--     `sources` were never compiled under `mcpp test` → link-time `undefined
+--     reference` (`mcpp build` was always fine). Fixed in mcpp 0.0.94; the same
+--     bug is what compat.cjson's `utils` and compat.eigen's `eigen_blas`
+--     (`dgemm_`) hit. Header-only mode is unaffected and works on any version,
+--     which is why the index floor (`index.toml` min_mcpp) does not move: that
+--     floor tracks descriptor GRAMMAR, and this descriptor parses everywhere.
+--
+-- All `mcpp` paths are GLOBS relative to the verdir; the leading `*` absorbs the
+-- GitHub archive's `spdlog-<tag>/` wrap layer. include_dirs points at
+-- `*/include` so consumers write `#include <spdlog/spdlog.h>`.
+--
+-- No CN mirror yet: `url` is a plain string (upstream GitHub release only), the
+-- documented fallback when there is no mcpp-res write access (docs/cn-mirror.md;
+-- precedent: pkgs/t/tensorvia-cpu.lua). CN users fall back to the upstream
+-- source. A maintainer can later rewrite each `url` to a { GLOBAL, CN } table
+-- (sha256 unchanged) once the gitcode mcpp-res/spdlog mirror exists.
+package = {
+    spec        = "1",
+    namespace   = "compat",
+    name        = "compat.spdlog",
+    description = "Fast C++ logging library (header-only by default, compiled via the `compiled` feature)",
+    licenses    = {"MIT"},
+    repo        = "https://github.com/gabime/spdlog",
+    type        = "package",
+
+    xpm = {
+        linux = {
+            ["1.17.0"] = {
+                url    = "https://github.com/gabime/spdlog/archive/refs/tags/v1.17.0.tar.gz",
+                sha256 = "d8862955c6d74e5846b3f580b1605d2428b11d97a410d86e2fb13e857cd3a744",
+            },
+        },
+        macosx = {
+            ["1.17.0"] = {
+                url    = "https://github.com/gabime/spdlog/archive/refs/tags/v1.17.0.tar.gz",
+                sha256 = "d8862955c6d74e5846b3f580b1605d2428b11d97a410d86e2fb13e857cd3a744",
+            },
+        },
+        windows = {
+            ["1.17.0"] = {
+                url    = "https://github.com/gabime/spdlog/archive/refs/tags/v1.17.0.tar.gz",
+                sha256 = "d8862955c6d74e5846b3f580b1605d2428b11d97a410d86e2fb13e857cd3a744",
+            },
+        },
+    },
+
+    mcpp = {
+        language     = "c++23",
+        import_std   = false,
+        c_standard   = "c11",
+        -- Exposes include/spdlog/** so consumers write `#include <spdlog/...>`.
+        -- The bundled fmt under include/spdlog/fmt/bundled/ rides along, so no
+        -- external fmt dependency is needed in either mode.
+        include_dirs = { "*/include" },
+        -- Header-only default: a trivial anchor TU gives mcpp a buildable lib
+        -- target when no source is compiled.
+        generated_files = {
+            ["mcpp_generated/spdlog_anchor.c"] = [==[
+int mcpp_compat_spdlog_headers_anchor(void) { return 0; }
+]==],
+        },
+        sources      = { "mcpp_generated/spdlog_anchor.c" },
+        targets      = { ["spdlog"] = { kind = "lib" } },
+        features     = {
+            -- Precompiled mode: compiles spdlog's src/*.cpp into the lib AND
+            -- publishes SPDLOG_COMPILED_LIB as an interface define so consumer
+            -- headers take the non-inline / extern-template path. src/spdlog.cpp
+            -- (and the other six) #error without this define. Needs mcpp >=
+            -- 0.0.94 under `mcpp test` — see the header note.
+            ["compiled"] = {
+                sources = { "*/src/*.cpp" },
+                defines = { "SPDLOG_COMPILED_LIB" },
+            },
+        },
+        deps         = { },
+    },
+}
diff --git a/tests/examples/spdlog-compiled/mcpp.toml b/tests/examples/spdlog-compiled/mcpp.toml
@@ -0,0 +1,19 @@
+# spdlog test project: consumes compat.spdlog in its COMPILED mode
+# (`features = ["compiled"]`) — spdlog's src/*.cpp are compiled into the lib and
+# SPDLOG_COMPILED_LIB reaches this consumer's TUs as an interface define, so the
+# headers take the non-inline path and link against those objects.
+#
+# Sibling of tests/examples/spdlog/ (header-only default mode). Both modes ship
+# from one descriptor; this member is what keeps the compiled path honest.
+#
+# Needs mcpp >= 0.0.94: older versions never compiled a dependency's active
+# feature `sources` under `mcpp test`, so this member would fail to link.
+[package]
+name = "spdlog-compiled-tests"
+version = "0.1.0"
+
+[indices]
+compat = { path = "../../.." }
+
+[dependencies.compat]
+spdlog = { version = "1.17.0", features = ["compiled"] }
diff --git a/tests/examples/spdlog-compiled/tests/compiled_test.cpp b/tests/examples/spdlog-compiled/tests/compiled_test.cpp
@@ -0,0 +1,42 @@
+// Behavioral test: consume compat.spdlog in COMPILED mode. Asserts both halves
+// of what the `compiled` feature promises:
+//
+//   1. the interface define reached this TU (SPDLOG_COMPILED_LIB defined, and
+//      spdlog's headers therefore did NOT flip on SPDLOG_HEADER_ONLY) — a
+//      static check, so a regression is a compile error, not a silent fallback
+//      to the header-only path that would still pass the runtime assertions;
+//   2. spdlog's src/*.cpp really were compiled and linked — the calls below
+//      resolve to out-of-line symbols (default_logger_raw, log_msg's ctor,
+//      logger::log_it_, and bundled fmt's vformat), which is exactly what fails
+//      to link when the engine skips a feature's sources.
+#include <spdlog/spdlog.h>
+#include <spdlog/sinks/ostream_sink.h>
+#include <sstream>
+#include <string>
+
+#ifndef SPDLOG_COMPILED_LIB
+#error "compiled feature did not propagate SPDLOG_COMPILED_LIB to the consumer"
+#endif
+#ifdef SPDLOG_HEADER_ONLY
+#error "SPDLOG_HEADER_ONLY is on in compiled mode — headers took the inline path"
+#endif
+
+int main() {
+    std::ostringstream captured;
+    auto sink = std::make_shared<spdlog::sinks::ostream_sink_mt>(captured);
+    spdlog::logger logger("test", sink);
+    logger.set_pattern("%v");  // message only, no timestamp/level decoration
+
+    logger.info("hello {}={}", "answer", 42);
+    logger.warn("{:#x}", 255);
+    logger.flush();
+
+    // Exercises the global registry too — default_logger_raw() is one of the
+    // out-of-line symbols that only exists once src/spdlog.cpp is compiled.
+    spdlog::set_level(spdlog::level::info);
+
+    const std::string out = captured.str();
+    const bool ok = out.find("hello answer=42") != std::string::npos
+                    && out.find("0xff") != std::string::npos;
+    return ok ? 0 : 1;
+}
diff --git a/tests/examples/spdlog/mcpp.toml b/tests/examples/spdlog/mcpp.toml
@@ -0,0 +1,15 @@
+# spdlog test project: consumes compat.spdlog in its DEFAULT header-only mode
+# (bundled fmt, no external dependency) and asserts behavior under `mcpp test`.
+# Part of the mcpp-index self-referential workspace: `[indices] compat` points
+# at this repo, so the dependency resolves to the checked-in recipe
+# (pkgs/c/compat.spdlog.lua). Compiled mode is covered by the sibling member
+# tests/examples/spdlog-compiled/.
+[package]
+name = "spdlog-tests"
+version = "0.1.0"
+
+[indices]
+compat = { path = "../../.." }
+
+[dependencies.compat]
+spdlog = "1.17.0"
diff --git a/tests/examples/spdlog/tests/log_test.cpp b/tests/examples/spdlog/tests/log_test.cpp
@@ -0,0 +1,25 @@
+// Behavioral test: consume compat.spdlog in its DEFAULT header-only mode. Logs
+// through a custom logger wired to an in-memory ostream sink, then asserts the
+// formatted output — this exercises the logger, the pattern formatter, and the
+// bundled {fmt} formatting all via the header inlines. Returns non-zero on any
+// mismatch.
+#include <spdlog/spdlog.h>
+#include <spdlog/sinks/ostream_sink.h>
+#include <sstream>
+#include <string>
+
+int main() {
+    std::ostringstream captured;
+    auto sink = std::make_shared<spdlog::sinks::ostream_sink_mt>(captured);
+    spdlog::logger logger("test", sink);
+    logger.set_pattern("%v");  // message only, no timestamp/level decoration
+
+    logger.info("hello {}={}", "answer", 42);
+    logger.warn("{:#x}", 255);
+    logger.flush();
+
+    const std::string out = captured.str();
+    const bool ok = out.find("hello answer=42") != std::string::npos
+                    && out.find("0xff") != std::string::npos;
+    return ok ? 0 : 1;
+}

Original file line number	Diff line number	Diff line change
`@@ -20,4 +20,6 @@ members = [`
`20`	`20`	`"tests/examples/nlohmann.json",`
`21`	`21`	`"tests/examples/openblas",`
`22`	`22`	`"tests/examples/opencv",`
	`23`	`+ "tests/examples/spdlog",`
	`24`	`+ "tests/examples/spdlog-compiled",`
`23`	`25`	`]`