CMake CPM Target Conflict 2: The Shadow Variable

---

# 🐛 CMake CPM Target Conflict 2: The Shadow Variable

## The Sequel to a Three-Hour Debugging Session 🎬

### From 11 Recommendations to 3 Compilation Errors to 1 Root Cause

@luk036 👨‍💻 · 2026 📅

---

### 📋 Agenda 🗺️

**Part 1: The Portfolio** 📦
- 28 Repos, One Sweep
- The Audit Findings

**Part 2: The 11 Recommendations** 📋
- Hygiene, Guards, Docs, CI
- The 3 fmt Guard Idioms

**Part 3: The Implementation** ⚙️
- The Mechanical Changes
- The Guard "Fix"

]

**Part 4: The Compilation Errors** 💥
- CPM Recursion
- fmt ALIAS Conflict
- absl IMPORTED vs REAL

**Part 5: Root Cause** 🕳️
- The Shadow Variable
- Minimal Reproduction

**Part 6: Fix & Lessons** ✅
- The CACHE-write Idiom
- 28 Repos Green

]

---

## 📦 Part 1: The Portfolio

---

### The Task: 28 C++ Repos at Once 🎯

- Audit the whole portfolio 🌐
- Suggest improvements 💡
- Implement ALL recommendations ⚙️
- Verify everything builds 🏗️

**The twist:** Every repo is a **header-only library** using:
- CMake + CPM.cmake
- doctest + GitHub Actions
- `find_package` first → CPM fallback
]

.pull-right[
.mermaid[
<pre>
graph TD
    subgraph Portfolio["28 C++ Repos"]
        P1["ckpttn-cpp"] --> P2["netlistx-cpp"]
        P2 --> P3["xnetwork-cpp"]
        P3 --> P4["py2cpp"]
        P1 --> P5["digraphx-cpp"]
        P5 --> P6["netoptim-cpp"]
        P6 --> P7["ellalgo-cpp"]
        P8["fractions-cpp"] --> P9["projgeom-cpp"]
        P9 --> P10["rat-trig-cpp"]
    end
    style Portfolio fill:#e8f5e9
    style P1 fill:#4caf50,color:#fff
    style P6 fill:#ff9800,color:#fff
    style P8 fill:#4caf50,color:#fff
</pre>
]
]

---

### The Audit: Everything Looked Healthy ✅

| Check | Result |
|-------|--------|
| Git repos | 27/28 (helloworld-cpp was not) |
| CMakeLists.txt | 28/28 |
| GitHub Actions CI | 27/28 (helloworld-cpp missing) |
| Test files | 28/28 (doctest) |
| README.md | 25/28 (lmi-solver, rat-trig-simple, helloworld missing) |
| Last commit | All within 48h 🔥 |
| Working tree | All clean |

]

**First impression:** A well-maintained, disciplined portfolio. 🎯

But a deeper look revealed **11 recommendations**...

---

## 📋 Part 2: The 11 Recommendations

---

### Rec 1–2: Hygiene First 🧹

**Rec 1: 26 tracked `.bak` files** in `.github/workflows/` across 16 repos

```
standalone.bak · style.bak · test.bak · benchmark.bak
```

All committed to git — zero reason to keep them. Deleted via `git rm`. 🗑️

**Rec 2: Broken CI badges** 🏷️

`digraphx-fast` and `digraphx-cpp` READMEs pointed at **`luk036/digraph-cpp`** — a repo that doesn't exist!

```markdown
❌ https://github.com/luk036/digraph-cpp/workflows/Ubuntu/badge.svg
✅ https://github.com/luk036/digraphx-fast/workflows/Ubuntu/badge.svg
```

---

### Rec 3: The fmt Guard — 3 Inconsistent Idioms ⚠️

Every repo does `find_package(fmt)` → CPM fallback. But the guard differs:

.mermaid[
<pre>
graph LR
    subgraph Idiom1["Idiom 1 — set(CPM_fmt_ADDED YES)"]
        A1["ecgen, lmi-solver, mywheel\npy2cpp, xnetwork, csd\nnetlistx, ellalgo"]
    end
    subgraph Idiom2["Idiom 2 — list(APPEND CPM_PACKAGES fmt)"]
        A2["corr-solver, multiplierless"]
    end
    subgraph Idiom3["Idiom 3 — No guard at all"]
        A3["ckpttn, ginger, netoptim\nprojgeom, sphere-n, digraphx\nphysdes"]
    end
    Idiom1 --> Q{"Which one\nis correct?"}
    Idiom2 --> Q
    Idiom3 --> Q
    Q --> R["❓ Ask CPM's source code..."]
    style Idiom1 fill:#fff3e0
    style Idiom2 fill:#fff3e0
    style Idiom3 fill:#fff3e0
    style Q fill:#ff9800,color:#fff
    style R fill:#e3f2fd
</pre>
]

---

### Rec 3: What CPM Actually Checks 🔍

The reference presentation taught us: **read the source, don't guess.**

.font-sm[
```cmake
# CPM 0.32.0 — cpm_check_if_package_already_added
function(cpm_check_if_package_already_added CPM_ARGS_NAME CPM_ARGS_VERSION)
  if("${CPM_ARGS_NAME}" IN_LIST CPM_PACKAGES)   # ← THIS is the check
    ...
    return()
  endif()
endfunction()
```
]

**Key insight:** `set(CPM_fmt_ADDED YES)` is a **no-op** — CPM never reads it!

So the plan was: **migrate everything to the `CPM_PACKAGES` idiom** and add it to the 7 unguarded repos.

---

### Rec 4–6: spdlog, Dead Code, Tests 🧩

**Rec 4: `SPDLOG_FMT_EXTERNAL` inconsistency**
- ecgen/csd/netlistx: **missing** entirely
- ckpttn: `ON` vs others: `YES`
- physdes: bare `SPDLOG_FMT_EXTERNAL` (no value!)

**Rec 5: Commented-out dead code** 🧟
Boost/cppcoro/GSL/xtensor blocks in 8 repos' `specific.cmake`

**Rec 6: Test file naming** 📁
11 different conventions found → standardized to `test_*.cpp`

---

### Rec 7–9: Docs, Outliers, CI 📚

**Rec 7: Missing READMEs**
- `lmi-solver-cpp`: only CI-enabled repo with no docs
- `rat-trig-simple`: empty README (0 bytes)

**Rec 8: `helloworld-cpp` outlier** 👽
No git, no CMake, no CI, no README → git-init + CMake + README + CI added

**Rec 9: Missing CI workflows**
- `netoptim-fast`: no `documentation.yaml`
- `lmi-solver-cpp`: no install/docs workflows

---

### Rec 10–11: Variants & Version Pins 🔗

**Rec 10: `-simple` / `-fast` variants** 🧬
6 variants on lighter CI sets → documented the difference in READMEs

**Rec 11: Cross-repo version pins** 🔐
24 pins verified — all tags exist, all consistent:

.mermaid[
<pre>
graph LR
    subgraph Producers["Producer Repos"]
        A["py2cpp\nv1.6.3"]
        B["ellalgo-cpp\nv1.6.8"]
        C["fractions-cpp\nv1.1.3"]
    end
    subgraph Consumers["Consumer Repos"]
        D["xnetwork, ecgen, mywheel..."]
        E["corr-solver, lmi-solver..."]
        F["projgeom, rat-trig"]
    end
    A --> D
    B --> E
    C --> F
    style Producers fill:#e8f5e9
    style Consumers fill:#e3f2fd
    style A fill:#4caf50,color:#fff
    style B fill:#4caf50,color:#fff
    style C fill:#4caf50,color:#fff
</pre>
]

---

## ⚙️ Part 3: The Implementation

---

### The Mechanical Sweep ⚡

All changes applied — nothing committed yet:

| Change | Scope |
|--------|-------|
| Delete `.bak` files | 26 files / 16 repos |
| Fix badges | 2 repos |
| Standardize fmt guard | 16 specific.cmake |
| Standardize spdlog flag | 6 repos |
| Remove dead code | 8 repos |
| Rename test file | 1 repo |
| Add READMEs | 2 repos |
| git-init + CMake helloworld | 1 repo |
| Add CI workflows | 3 repos |
| Document variants | 10 READMEs |

]

**Total: all 28 repos touched.** 🎉

---

### The Guard "Fix" — My Mistake 🔥

I applied the `CPM_PACKAGES` guard everywhere:

.font-sm[
```cmake
find_package(fmt CONFIG QUIET)
if(fmt_FOUND)
  message(STATUS "Found system fmt: ${fmt_DIR}")
  if(NOT fmt IN_LIST CPM_PACKAGES)
    list(APPEND CPM_PACKAGES fmt)     # ← My "fix"
  endif()
else()
  CPMAddPackage(NAME fmt ...)
endif()
```
]

**It compiled everywhere... in theory.** 🤔

The reference doc warned: *"CPM_PACKAGES from parent scope might not propagate to FetchContent's subdirectory scope"* 🔴

**I treated that as a hint. It was a trap.**

---

## 💥 Part 4: The Compilation Errors

---

### Error 1: CPM Recursion — ckpttn-cpp 💀

```
CMake Error at CPM_0.32.0.cmake:784 (string):
  Maximum recursion depth of 1000 exceeded
Call Stack:
  CPM_0.32.0.cmake:390 (cpm_get_version_from_git_tag)
  FindPy2Cpp.cmake:2 (CPMAddPackage)
  CPM_0.32.0.cmake:204 (find_package)
  CPM_0.32.0.cmake:490 (cpm_find_package)
  FindPy2Cpp.cmake:2 (CPMAddPackage)   # ← loop!
```

.mermaid[
<pre>
graph LR
    A["CPMAddPackage\n(Py2Cpp)"] --> B{"Py2Cpp IN_LIST\nCPM_PACKAGES?"}
    B -- "No ❌" --> C["cpm_find_package"]
    C --> D["find_package(Py2Cpp)"]
    D --> E["FindPy2Cpp.cmake\n(generated module)"]
    E --> A
    style A fill:#ff9800,color:#fff
    style B fill:#f44336,color:#fff
    style C fill:#f44336,color:#fff
    style D fill:#f44336,color:#fff
    style E fill:#f44336,color:#fff
</pre>
]

---

### Error 2: fmt ALIAS Conflict — netoptim-fast 💥

**The EXACT error from the reference presentation:**

```
CMake Error at fmt/CMakeLists.txt:309 (add_library):
  add_library cannot create ALIAS target "fmt::fmt" because another
  target with the same name already exists.
```

.mermaid[
<pre>
graph LR
    A["netoptim-fast specific.cmake\nfind_package(fmt) → system"] --> B["fmt::fmt = IMPORTED ✅"]
    C["fetched DiGraphXFast\nCPMAddPackage(fmt) unguarded"] --> D["CPM fetches fmt\ncreates fmt::fmt ALIAS"]
    B --> E["CONFLICT 💥"]
    D --> E
    style A fill:#e3f2fd
    style B fill:#4caf50,color:#fff
    style C fill:#fff3e0
    style D fill:#ff9800,color:#fff
    style E fill:#f44336,color:#fff
</pre>
]

**Was this MY bug?** 🤔 My changes to netoptim-fast were only README + workflows...

---

### Error 3: absl IMPORTED vs REAL — netoptim-cpp 💢

```
CMake Error at .../absl/abslTargets.cmake:42 (message):
  Some (but not all) targets in this export set were already defined.
```

.mermaid[
<pre>
graph TD
    A["netoptim-cpp specific.cmake"] --> B["CPMAddPackage(DiGraphX)"]
    B --> C["DiGraphX CPM-adds abseil-cpp\n→ REAL absl::* targets"]
    A --> D["find_package(absl)\nconda system absl"]
    D --> E["→ IMPORTED absl::* targets"]
    C --> F["CONFLICT 💥\nREAL vs IMPORTED"]
    E --> F
    style A fill:#e3f2fd
    style B fill:#fff3e0
    style C fill:#ff9800,color:#fff
    style D fill:#fff3e0
    style E fill:#ff9800,color:#fff
    style F fill:#f44336,color:#fff
</pre>
]

---

### Which Errors Are MINE? 🕵️

The reference doc's lesson: *"Each project has a different dependency chain — one pattern doesn't fit all."*

I ran a **stash test**: revert my changes → reconfigure → observe.

| Repo | Error | Mine? |
|------|-------|-------|
| ckpttn-cpp | CPM recursion | ✅ **Mine** (list(APPEND)) |
| xnetwork-cpp | CPM recursion | ✅ **Mine** |
| netoptim-cpp | CPM recursion | ✅ **Mine** |
| netoptim-fast | fmt ALIAS conflict | ❌ Pre-existing (committed code) |
| netoptim-cpp | absl IMPORTED vs REAL | ❌ Pre-existing |
| netlistx-cpp | LNK2038 | ❌ Stale Debug/Release cache artifact |

]

**Important:** Only fix MY regressions first — but the user asked for ALL local errors fixed. So both classes had to be solved. 🎯

---

## 🕳️ Part 5: Root Cause — The Shadow Variable

---

### CPM_PACKAGES is a CACHE INTERNAL Variable 📦

.font-sm[
```cmake
# CPM 0.32.0 — at the top of the file
set(CPM_PACKAGES
    ""
    CACHE INTERNAL ""          # ← CACHE INTERNAL
)

# CPMRegisterPackage — after adding a package
function(CPMRegisterPackage PACKAGE VERSION)
  list(APPEND CPM_PACKAGES ${PACKAGE})
  set(CPM_PACKAGES ${CPM_PACKAGES} CACHE INTERNAL "")   # ← updates the cache
endfunction()
```
]

**`CACHE INTERNAL` = visible everywhere, in every scope.** 🌍

So why didn't my `list(APPEND ...)` work?

---

### list(APPEND) Creates a Shadow 🪤

**The bug is subtle:**

.font-sm[
```cmake
# My code in specific.cmake (top-level scope)
if(NOT fmt IN_LIST CPM_PACKAGES)
  list(APPEND CPM_PACKAGES fmt)    # ← reads cache "", creates NORMAL var
endif()
```
]

`list(APPEND)` on a cache variable:
1. Reads the cache value → `""`
2. Creates a **NORMAL variable** `CPM_PACKAGES = [fmt]` in the current directory scope
3. The normal variable **shadows** the cache — in this scope AND all child scopes

.mermaid[
<pre>
graph TD
    A["list(APPEND CPM_PACKAGES fmt)"] --> B["Reads CACHE = empty"]
    B --> C["Creates NORMAL var\nCPM_PACKAGES = [fmt]"]
    C --> D["NORMAL var shadows CACHE\nin current + child scopes"]
    style A fill:#ff9800,color:#fff
    style B fill:#e3f2fd
    style C fill:#f44336,color:#fff
    style D fill:#f44336,color:#fff
</pre>
]

---

### Why FetchContent Breaks It 🧵

`CPMAddPackage` fetches deps via **FetchContent → add_subdirectory** — a CHILD scope.

The child scope inherits the **normal-variable shadow** `[fmt]`, NOT the cache `[fmt;Py2Cpp]`:

.mermaid[
<pre>
graph TD
    subgraph Parent["Parent Scope (specific.cmake)"]
        N1["NORMAL var: [fmt]\n(shadow, from my list(APPEND))"]
    end
    subgraph Cache["CACHE INTERNAL (global)"]
        C1["[fmt;Py2Cpp]\n(CPM registered Py2Cpp here)"]
    end
    subgraph Child["FetchContent subdirectory\n(fetched dep's specific.cmake)"]
        Q{"Py2Cpp IN_LIST\nCPM_PACKAGES?"}
    end
    N1 -->|"inherited ↓"| Q
    C1 -.->|"shadowed ✗"| Q
    Q -->|"No → recursion 💥"| R["find_package(Py2Cpp)\n→ FindPy2Cpp.cmake\n→ CPMAddPackage\n→ infinite loop"]
    style N1 fill:#f44336,color:#fff
    style C1 fill:#4caf50,color:#fff
    style Q fill:#ff9800,color:#fff
    style R fill:#f44336,color:#fff
</pre>
]

---

### Minimal Reproduction — Proven in 60 Seconds ⏱️

I wrote a tiny CMake test to **prove** the mechanism before touching 16 files:

.font-sm[
```cmake
# CMakeLists.txt (parent)
set(CPM_PACKAGES "" CACHE INTERNAL "")
if(NOT fmt IN_LIST CPM_PACKAGES)
  list(APPEND CPM_PACKAGES fmt)         # ← the shadow
endif()
function(CPMRegisterPackage PACKAGE VERSION)
  list(APPEND CPM_PACKAGES ${PACKAGE})
  set(CPM_PACKAGES ${CPM_PACKAGES} CACHE INTERNAL "")
endfunction()
CPMRegisterPackage(Py2Cpp v1.6.3)
add_subdirectory(sub)                    # ← child scope
```
]

.font-sm[
```cmake
# sub/CMakeLists.txt (child = FetchContent scope)
if(Py2Cpp IN_LIST CPM_PACKAGES)
  message(STATUS "Py2Cpp FOUND — GOOD")
else()
  message(STATUS "Py2Cpp NOT in list — RECURSION RISK")
endif()
```
]

---

### The Shadow Test Verdict 🧪

**`list(APPEND)` result — RECURSION CONFIRMED:**

.font-sm[
```text
-- PARENT scope CPM_PACKAGES = [fmt]
-- PARENT after register = [fmt] cache=[fmt;Py2Cpp]
--   SUB scope CPM_PACKAGES = [fmt]
--   SUB: Py2Cpp NOT in list -> RECURSION RISK   ❌
```
]

**`set(... CACHE ... FORCE)` result — CORRECT:**

.font-sm[
```text
-- PARENT scope CPM_PACKAGES = [;fmt]
-- PARENT after register = [fmt;Py2Cpp]
--   SUB scope CPM_PACKAGES = [fmt;Py2Cpp]
--   SUB: Py2Cpp FOUND in list - GOOD            ✅
```
]

**Root cause proven:** `list(APPEND)` on a `CACHE INTERNAL` var = normal-var shadow = broken across FetchContent scopes. 🎯

---

## ✅ Part 6: The Fix

---

### The Correct Idiom: Write the CACHE Directly 💪

.font-sm[
```cmake
# ❌ BROKEN: creates a normal-variable shadow
if(NOT fmt IN_LIST CPM_PACKAGES)
  list(APPEND CPM_PACKAGES fmt)
endif()

# ✅ CORRECT: writes the CACHE INTERNAL variable directly
if(NOT fmt IN_LIST CPM_PACKAGES)
  set(CPM_PACKAGES "${CPM_PACKAGES};fmt" CACHE INTERNAL "" FORCE)
endif()
```
]

**`FORCE`** overwrites any existing cache value. No normal variable is created — the value propagates into every FetchContent child scope. 🌍

Applied to **18 specific.cmake files** (16 with the guard + netoptim-fast + netoptim-cpp).

---

### netoptim-cpp absl Fix — Don't Mix! 🎭

Per the reference doc: *"you cannot mix `find_package` and `CPMAddPackage` for the same dependency."*

DiGraphX already CPM-adds abseil → check for the REAL target first:

.font-sm[
```cmake
# If DiGraphX already added abseil via CPM, use its REAL targets
if(TARGET absl::flat_hash_map)
  message(STATUS "Using CPM-provided abseil (from DiGraphX)")
  set(SPECIFIC_ABSEIL_LIBS absl::flat_hash_map)
else()
  find_package(absl CONFIG QUIET)     # ← only when NOT already provided
  ...
endif()
```
]

**No more IMPORTED vs REAL collision.** 🧹

---

### Verification: All 28 Repos Build 🏁

Fresh configure + build for EVERY repo (no stale caches):

| Repo | Before | After |
|------|:------:|:-----:|
| ckpttn-cpp | ❌ recursion | ✅ build |
| xnetwork-cpp | ❌ recursion | ✅ build |
| netoptim-cpp | ❌ recursion + absl | ✅ build |
| netoptim-fast | ❌ fmt ALIAS | ✅ build |
| all 24 others | ✅ / untested | ✅ build |

]

**28/28 repos configure AND compile from scratch.** 🎉

---

### What I Could Have Done Faster ⏳

- 🔥 **1 wrong assumption** → the `list(APPEND)` idiom
- 🕵️ **2 pre-existing bugs** I had to prove weren't mine
- 🏗️ **28 fresh builds** × 2 (find errors + verify fix)
- ⏱️ ~1 hour of pure machine time

]

- 📖 Read the reference's Attempt 5 as a **constraint**, not a hint
- 🧪 Write the minimal repro **before** editing 16 files
- 🔍 Check `git status` first to isolate my changes from committed code

]

> "It took 6 attempts because I treated all projects the same. They weren't the same." 🎯

---

## 🎯 Key Takeaways

---

### Lessons Learned 📝

1. **`list(APPEND)` on a CACHE variable is a shadow trap** 🪤
   It creates a normal variable that hides the cache from child scopes. Use `set(... CACHE INTERNAL "" FORCE)` instead.

2. **FetchContent scoping is the real enemy** 🧵
   `add_subdirectory` inherits normal vars, not your intent.

3. **Distinguish YOUR bugs from pre-existing ones** 🕵️
   Stash → revert → reconfigure. Fix your regression first, then the rest.

4. **Reference docs list failed attempts for a reason** 📖
   "Couldn't test due to scoping" was a RED FLAG, not a TODO.

5. **Prove the mechanism before mass edits** 🧪
   A 60-second minimal reproduction beats 16 broken files.

6. **Verification on 28 repos is inherently slow** ⏱️
   Budget for machine time, not just decision time.

---

### The One-Slide Summary 🔑

.mermaid[
<pre>
graph TD
    A["I applied\nlist(APPEND CPM_PACKAGES fmt)"] --> B["Normal-var shadow\nhides cache in child scopes"]
    B --> C["Fetched dep checks CPM_PACKAGES\n→ Py2Cpp not found"]
    C --> D["find_package → FindPy2Cpp.cmake\n→ CPMAddPackage → recursion 💥"]
    D --> E["Fix: set(... CACHE INTERNAL '' FORCE)"]
    E --> F["Value propagates everywhere\n28 repos build ✅"]
    style A fill:#fff3e0
    style B fill:#ff9800,color:#fff
    style C fill:#f44336,color:#fff
    style D fill:#f44336,color:#fff
    style E fill:#4caf50,color:#fff
    style F fill:#4caf50,color:#fff
</pre>
]

**One wrong CMake idiom → 3 error classes → 28 repos to verify.** 🎬

---

### When `list(APPEND)` Meets `CACHE INTERNAL` 🧪

list(APPEND MY_LIST a)          # creates NORMAL var shadow = [a]
set(MY_LIST "${MY_LIST};a" CACHE INTERNAL "" FORCE)  # updates cache directly
```
]

| Operation | Parent reads | Child reads | Verdict |
|-----------|:------------:|:-----------:|:-------:|
| `list(APPEND MY_LIST a)` | `[a]` (shadow) | `[a]` (shadow) | ❌ cache hidden |
| `set(... CACHE INTERNAL "" FORCE)` | `[;a]` (cache) | `[a;b]` (cache) | ✅ propagates |

**Rule of thumb:** when in doubt, write the CACHE variable directly. 🔑

---

### The Real Lesson 🧠

.mermaid[
<pre>
graph TD
    subgraph Cost["Cost of Guessing 🔥"]
        G1["❌ 3 error classes"] --> G2["❌ 28 repos × 2 builds"]
        G2 --> G3["❌ 1 hour machine time"]
    end
    subgraph Better["Better Approach 💡"]
        B1["✅ Stop. Read CPM source."] --> B2["✅ Treat doc warnings as constraints"]
        B2 --> B3["✅ Minimal repro first"]
        B3 --> B4["✅ Isolate my bugs via git stash"]
        B4 --> B5["✅ Apply ONE correct idiom"]
    end
    Cost --> Better
    style Cost fill:#fce4ec,stroke:#f44336
    style Better fill:#e8f5e9,stroke:#4caf50
    style G1 fill:#f44336,color:#fff
    style G2 fill:#f44336,color:#fff
    style G3 fill:#f44336,color:#fff
    style B1 fill:#4caf50,color:#fff
    style B2 fill:#4caf50,color:#fff
    style B3 fill:#4caf50,color:#fff
    style B4 fill:#4caf50,color:#fff
    style B5 fill:#4caf50,color:#fff
</pre>
]

---

### Why Did It Take So Long? ⏰

- 🔥 My own mistake: 1 wrong idiom applied to 16 files
- 🕵️ Proving pre-existing bugs weren't mine: stash tests + clean rebuilds
- 🏗️ Verification cost: 28 repos × 2 fresh builds each
- ⚠️ Two false leads: stale-cache link error, benign pthread probes

]

- 20% of the time → writing the fixes
- 80% of the time → **proving which errors were mine** and **verifying the fix** across 28 repos

> "The fixes themselves were the small part." 💡
]

---

# 🙏 Thank You

## Questions? 🎤

### **"Write the CACHE. Don't shadow it. Verify everything."**

Slides: `luk036.github.io/proglang/cmake-conflict2-remark.html`

---

# 👋 That's All Folks!

## **28 Repos, 11 Recommendations, 3 Errors, 1 Root Cause** 🚀

### `set(CPM_PACKAGES "…;fmt" CACHE INTERNAL "" FORCE)` ✅