// mcpp#344 — a package's object addresses must be a function of that package

// alone.

//

// This is the machine-checkable form of the invariant the global build cache

// depends on. The cache key deliberately excludes the consuming project (that

// is what makes an entry shareable across projects), so if a dependency's

// object layout can shift when the consumer pulls in some UNRELATED package,

// two consumers write and read incompatible layouts under one key. #344 was

// exactly that: `compat.zlib`'s compress.o was `obj/compress.o` alone and

// `obj/compat_zlib/zlib-1.3.2/compress.o` alongside `compat.bzip2` (which ships

// its own compress.c), because basename disambiguation (#233) was driven by a

// census over every unit in the build.

//

// The test therefore builds the SAME dependency twice — once alone, once beside

// a package engineered to collide with it — and demands byte-identical

// addresses. It fails on the pre-#344 tree.

#include <gtest/gtest.h>

import std;

import mcpp.build.plan;

import mcpp.manifest;

import mcpp.modgraph.graph;

import mcpp.modgraph.scanner;

import mcpp.toolchain.model;

using namespace mcpp::build;

namespace {

struct Tmp {

std::filesystem::path path;

Tmp() {

path = std::filesystem::temp_directory_path()

/ std::format("mcpp_obj_addr_{}", std::random_device{}());

std::filesystem::create_directories(path);

}

~Tmp() {

std::error_code ec;

std::filesystem::remove_all(path, ec);

}

};

void touchFile(const std::filesystem::path& p) {

std::filesystem::create_directories(p.parent_path());

std::ofstream(p) << "/* test */\n";

}

mcpp::toolchain::Toolchain gccLike() {

mcpp::toolchain::Toolchain tc;

tc.compiler = mcpp::toolchain::CompilerId::GCC;

tc.version = "16.1.0";

tc.binaryPath = "/usr/bin/g++";

tc.targetTriple = "x86_64-linux-gnu";

return tc;

}

mcpp::modgraph::PackageRoot makePackage(const std::filesystem::path& root,

std::string_view name) {

mcpp::modgraph::PackageRoot p;

p.root = root;

p.manifest.package.name = std::string(name);

p.manifest.package.version = "1.0.0";

p.manifest.package.standard = "c++23";

return p;

}

// One C source per package, all sharing the basename `compress.c` — the shape

// that used to trigger the global census.

mcpp::modgraph::SourceUnit unitFor(const std::filesystem::path& pkgRoot,

const std::filesystem::path& rel,

std::string_view pkgName) {

mcpp::modgraph::SourceUnit u;

u.path = pkgRoot / rel;

u.relPath = rel;

u.packageName = std::string(pkgName);

touchFile(u.path);

return u;

}

struct Built {

std::filesystem::path object;

std::filesystem::path packageObjectRel;

};

// Plan a graph containing the root project plus `deps`, and return the

// addresses computed for the FIRST dependency's single unit.

std::optional<Built> planZlib(const Tmp& t, bool withBzip2, std::string* err) {

auto projectRoot = t.path / "proj";

auto storeRoot = t.path / "store";

mcpp::manifest::Manifest rootManifest;

rootManifest.package.name = "app";

rootManifest.package.version = "0.1.0";

rootManifest.package.standard = "c++23";

mcpp::manifest::Target lib;

lib.name = "app";

lib.kind = mcpp::manifest::Target::Library;

rootManifest.targets.push_back(lib);

std::vector<mcpp::modgraph::PackageRoot> packages;

auto rootPkg = makePackage(projectRoot, "app");

rootPkg.manifest = rootManifest;

packages.push_back(rootPkg);

packages.push_back(makePackage(storeRoot / "compat.zlib@1.3.2", "compat.zlib"));

if (withBzip2)

packages.push_back(

makePackage(storeRoot / "compat.bzip2@1.0.8", "compat.bzip2"));

mcpp::modgraph::Graph graph;

graph.units.push_back(unitFor(projectRoot, "src/app.cpp", "app"));

graph.units.push_back(

unitFor(packages[1].root, "zlib-1.3.2/compress.c", "compat.zlib"));

if (withBzip2)

graph.units.push_back(

unitFor(packages[2].root, "bzip2-1.0.8/compress.c", "compat.bzip2"));

std::vector<std::size_t> topo;

for (std::size_t i = 0; i < graph.units.size(); ++i) topo.push_back(i);

auto plan = make_plan(rootManifest, gccLike(), {}, graph, topo, packages,

projectRoot, projectRoot / "target" / "t",

{}, {}, {storeRoot});

if (!plan) { if (err) *err = plan.error(); return std::nullopt; }

auto want = packages[1].root / "zlib-1.3.2" / "compress.c";

for (auto& cu : plan->compileUnits) {

if (cu.source != want) continue;

return Built{cu.object, cu.packageObjectRel};

}

if (err) *err = "zlib compile unit not found in the plan";

return std::nullopt;

}

} // namespace

// The load-bearing assertion. Adding an unrelated, deliberately colliding

// package to the graph must not move zlib's object by one byte — not its build

// path, and above all not its cache address.

TEST(ObjectAddress, DependencyAddressesAreImmuneToTheRestOfTheGraph) {

Tmp t;

std::string errAlone, errBeside;

auto alone = planZlib(t, /*withBzip2=*/false, &errAlone);

auto beside = planZlib(t, /*withBzip2=*/true, &errBeside);

ASSERT_TRUE(alone) << errAlone;

ASSERT_TRUE(beside) << errBeside;

EXPECT_EQ(alone->packageObjectRel, beside->packageObjectRel)

<< "the cache-entry address moved when an unrelated package joined the "

"graph — that is mcpp#344";

EXPECT_EQ(alone->object, beside->object);

}

// The address must also be package-internal: nothing about the consumer, and

// nothing that only exists on this machine. It is read back by another machine

// that computed the same key.

TEST(ObjectAddress, DependencyCacheAddressIsPackageInternal) {

Tmp t;

std::string err;

auto built = planZlib(t, /*withBzip2=*/true, &err);

ASSERT_TRUE(built) << err;

auto rel = built->packageObjectRel.generic_string();

EXPECT_FALSE(rel.empty());

EXPECT_FALSE(built->packageObjectRel.is_absolute()) << rel;

EXPECT_FALSE(rel.starts_with("..")) << rel;

// Mirrors the source's path relative to its OWN package root, and carries

// no package-partition component (that lives in the build path only).

EXPECT_EQ(rel, "zlib-1.3.2/compress.o") << rel;

// The build path does partition by package — that is what makes the

// cross-package census unnecessary.

auto obj = built->object.generic_string();

EXPECT_EQ(obj, "obj/compat_zlib/zlib-1.3.2/compress.o") << obj;

}

// `path_is_under_any` decides both whether a package may be cached and where

// its objects are anchored, and it must answer LEXICALLY.

//

// A payload store whose entries are symlinks into another store is ordinary:

// tests/e2e/_inherit_toolchain.sh builds one so an isolated MCPP_HOME can reuse

// the developer's toolchains, and CI caches do the same to avoid re-downloading.

// std::filesystem::relative() runs weakly_canonical and resolves those links, at

// which point `<home>/registry/data/xpkgs/<pkg>` no longer looks like it is in

// the store — every such package silently drops out of the build cache. That

// regression was caught by e2e 40 and is pinned here where it is cheap.

TEST(ObjectAddress, PathContainmentIsLexicalSoSymlinkedStoresStillCount) {

Tmp t;

auto real = t.path / "real-store";

auto store = t.path / "home" / "registry" / "data" / "xpkgs";

std::filesystem::create_directories(real / "compat.zlib@1.3.2" / "src");

std::filesystem::create_directories(store);

std::error_code ec;

std::filesystem::create_directory_symlink(

real / "compat.zlib@1.3.2", store / "compat.zlib@1.3.2", ec);

if (ec) GTEST_SKIP() << "symlinks unavailable: " << ec.message();

auto pkgRoot = store / "compat.zlib@1.3.2";

EXPECT_TRUE(path_is_under_any(pkgRoot, {store}));

EXPECT_TRUE(path_is_under_any(pkgRoot / "src" / "compress.c", {store}));

// And it still says no to something genuinely outside — the gate has to

// keep rejecting `target/.mangled/**`, which is the case it exists for.

EXPECT_FALSE(path_is_under_any(t.path / "proj" / "target" / ".mangled" / "x",

{store}));

EXPECT_FALSE(path_is_under_any(pkgRoot, {}));

}

// The root project is never cached, so it keeps the flat layout every project

// has had since 0.0.1 — and a dependency shipping a same-named file can no

// longer force it to disambiguate.

TEST(ObjectAddress, RootObjectsStayFlatAndUncacheable) {

Tmp t;

auto projectRoot = t.path / "proj";

auto storeRoot = t.path / "store";

mcpp::manifest::Manifest rootManifest;

rootManifest.package.name = "app";

rootManifest.package.version = "0.1.0";

rootManifest.package.standard = "c++23";

mcpp::manifest::Target lib;

lib.name = "app";

lib.kind = mcpp::manifest::Target::Library;

rootManifest.targets.push_back(lib);

std::vector<mcpp::modgraph::PackageRoot> packages;

auto rootPkg = makePackage(projectRoot, "app");

rootPkg.manifest = rootManifest;

packages.push_back(rootPkg);

packages.push_back(makePackage(storeRoot / "compat.zlib@1.3.2", "compat.zlib"));

mcpp::modgraph::Graph graph;

// Root ships its own compress.c, colliding with the dependency's.

graph.units.push_back(unitFor(projectRoot, "src/compress.c", "app"));

graph.units.push_back(

unitFor(packages[1].root, "zlib-1.3.2/compress.c", "compat.zlib"));

std::vector<std::size_t> topo{0, 1};

auto plan = make_plan(rootManifest, gccLike(), {}, graph, topo, packages,

projectRoot, projectRoot / "target" / "t",

{}, {}, {storeRoot});

ASSERT_TRUE(plan) << plan.error();

for (auto& cu : plan->compileUnits) {

if (cu.source == projectRoot / "src" / "compress.c") {

EXPECT_EQ(cu.object.generic_string(), "obj/compress.o");

EXPECT_TRUE(cu.packageObjectRel.empty())

<< "the root project must never get a cache address";

}

}

}