the note about a declared absence was missing a closing parenthesis

Every reader of it saw:

    note: the C library in this graph (musl declares that it does not supply

The C library's name was interpolated from two separate conditionals --- an
opening paren, then the name --- and the closing one was never emitted. It is
one substitution now.

NINE UNIT TESTS COVERED THIS FUNCTION AND NONE OF THEM SAW IT. They asserted
`a.find("musl")`, which is true of the broken spelling as well: a criterion
aimed at a substring of a sentence cannot see the sentence. The test now
asserts the rendered clause, and a second one covers the other side of the
same substitution --- an unnamed C library must leave no empty parentheses
rather than `graph () declares`.

WHAT ACTUALLY FOUND IT was running a real link. The nine unit tests covered
the matching rules and the sidecar round-trip, and seven more covered parsing
the table, but nothing ran the two together: that a real build writes the
sidecar beside build.ninja, that a real link failure reads it back, and that
what arrives is a sentence. e2e 744 does that, in four legs --- the linker's
own message survives, the row's note reaches it, the sentence reads as one,
and an absence is not reported as a defect in the build. Restoring the missing
paren fails the third and only the third.

The symbol the test uses is one nothing defines. `fork` is the real row in
openkal-musl's manifest and every C library on a Linux host defines it, so a
test written with it would link and assert nothing.

Author: speak-agent

CHANGELOG.md

@@ -105,6 +105,13 @@ tcsetattr = { form = "accepted-no-effect", note = "openkal 不命名的那些字
 的东西。链接点到 `link` 形状里的某一项时,mcpp 把清单读回来:`undefined reference to
 'fork'` 因此带着那句说明它是缺陷还是环境限制的话一起到达。
 
+**这条说明此前少一个右括号,而九个单测都没看见。** 渲染出来是
+`the C library in this graph (musl declares that it does not supply ...`——C 库的名字由
+**两个各自独立的条件**插进去:一个左括号,然后是名字,右括号从来没有被发出过。单测断言的
+是 `find("musl")`,那句话里同样有 "musl"。**判据瞄准一句话的子串,就看不见这句话。**
+修法是整个括号部分只做一次替换;新增的 e2e 744 真跑一次链接失败并断言整句,把右括号去掉
+它就红。
+
 **它是顶层表,而这是量出来的。** 先写成 `[c-abi].absent`——更顺——之后拿**真正发布的
 2026.9.18.3 归档**(当时的索引 floor)跑 openkal-musl 0.17.0 将要发布的那份清单:嵌套
 写法让每个旧 mcpp **在每个目标上拒绝整份清单**,报 `[c-abi] has no member 'absent'`。

src/build/ninja_backend.cppm

@@ -785,16 +785,22 @@ std::string c_abi_absent_facility_advice(
     }
     if (named.empty()) return {};
 
+    // ONE SUBSTITUTION FOR THE WHOLE PARENTHETICAL, not an opening paren and
+    // a name from two separate conditionals. Written that way, the closing
+    // paren was simply absent and every reader saw `(musl declares that it
+    // does not supply ...`. The unit tests asserted `find("musl")`, which is
+    // true of both spellings; it took running a real link to see it.
+    const std::string who =
+        cAbiName.empty() ? std::string{} : std::format(" ({})", cAbiName);
     return std::format(
         "\n"
-        "note: the C library in this graph{}{} declares that it does not "
+        "note: the C library in this graph{} declares that it does not "
         "supply the following, and the link has just asked for it:{}\n"
         "      An absence stated in the manifest is a property of the "
         "environment this program was built for, not a defect in the build. "
         "A program that needs one of these needs a different C environment "
         "for this target.\n",
-        cAbiName.empty() ? "" : " (", cAbiName.empty() ? "" : cAbiName,
-        named);
+        who, named);
 }
 
 std::string graph_c_library_isolation_advice(std::string_view output,

tests/e2e/744_a_declared_absence_explains_the_link_that_asked_for_it.sh

@@ -0,0 +1,110 @@
+#!/usr/bin/env bash
+# requires: gcc
+# 744 -- a `[c-abi-absent]` row with `form = "link"` reaches the LINK, and the
+# note it produces is read by a person.
+#
+# WHAT WAS UNTESTED, AND WHAT IT COST. `c_abi_absent_facility_advice` had nine
+# unit tests covering the matching rules and the sidecar round-trip, and the
+# table had seven covering the manifest. Nothing ran the two together: that a
+# real build WRITES the sidecar beside build.ninja, that a real link failure
+# READS it back, and that what arrives is a sentence.
+#
+# It was not a sentence. The C library's name was interpolated from two
+# separate conditionals -- an opening paren, then the name -- and the closing
+# paren was never emitted, so every reader saw
+#
+#     note: the C library in this graph (musl declares that it does not supply
+#
+# The unit test asserted `find("musl")`, which is true of that spelling too.
+# A criterion aimed at a substring of a sentence cannot see the sentence.
+#
+# THE SYMBOL IS DELIBERATELY ONE NOTHING DEFINES. `fork` is the real row in
+# openkal-musl's manifest and is defined by every C library on a Linux host,
+# so a test written with it would link and assert nothing.
+set -e
+
+MCPP="${MCPP:-mcpp}"
+work="$(mktemp -d)"
+trap 'rm -rf "$work"' EXIT
+cd "$work"
+
+mkdir -p libc/src src
+cat > libc/src/lib.c <<'EOF'
+int fake_c_library_marker(void) { return 0; }
+EOF
+cat > src/main.c <<'EOF'
+extern int mcpp_absent_probe_fn(void);
+int main(void) { return mcpp_absent_probe_fn(); }
+EOF
+cat > mcpp.toml <<'EOF'
+[package]
+name    = "absence-explains-the-link"
+version = "0.1.0"
+
+[targets.absence-explains-the-link]
+kind = "bin"
+main = "src/main.c"
+
+[dependencies]
+fakelibc = { path = "libc" }
+
+[build]
+allow_host_libs = true
+EOF
+cat > libc/mcpp.toml <<'EOF'
+[package]
+name     = "fakelibc"
+version  = "0.1.0"
+provides = ["mcpp:c-abi=musl"]
+
+[targets.fakelibc]
+kind    = "lib"
+sources = ["src/*.c"]
+
+[c-abi-absent]
+mcpp_absent_probe_fn = { form = "link", note = "this environment has no such operation" }
+EOF
+
+out="$("$MCPP" build 2>&1)" && {
+    echo "FAIL: the link must fail -- nothing defines mcpp_absent_probe_fn" >&2
+    echo "$out" >&2
+    exit 1
+}
+
+# ── A. the linker's own message is still there, unreplaced ─────────────────
+echo "$out" | grep -qi "mcpp_absent_probe_fn" || {
+    echo "FAIL: the linker's own diagnostic must survive" >&2
+    echo "$out" >&2
+    exit 1
+}
+echo "OK: A (the linker still reports the symbol)"
+
+# ── B. the manifest row reached the link ───────────────────────────────────
+echo "$out" | grep -q "this environment has no such operation" || {
+    echo "FAIL: the [c-abi-absent] row's note must reach the link diagnostic." \
+         "The sidecar is written beside build.ninja during the build and read" \
+         "back when the link fails; one of those two did not happen." >&2
+    echo "$out" >&2
+    exit 1
+}
+echo "OK: B (the row's note reached the failure)"
+
+# ── C. the sentence reads as a sentence ────────────────────────────────────
+# THE WHOLE CLAUSE, NOT A SUBSTRING OF IT. This is the assertion the unit
+# test did not make, and the defect it did not see.
+echo "$out" | grep -q "the C library in this graph (musl) declares that it does not supply" || {
+    echo "FAIL: the note must name the C library in a closed parenthetical." >&2
+    echo "     got: $(echo "$out" | grep -m1 'the C library in this graph')" >&2
+    exit 1
+}
+echo "OK: C (the note names the C library and reads as a sentence)"
+
+# ── D. an absence is not reported as a defect in the build ─────────────────
+echo "$out" | grep -q "not a defect in the build" || {
+    echo "FAIL: the note must say an absence is a property of the environment" >&2
+    echo "$out" >&2
+    exit 1
+}
+echo "OK: D (the note distinguishes an absence from a defect)"
+
+echo "OK"

tests/unit/test_build_flags.cpp

@@ -228,7 +228,27 @@ TEST(CAbiAbsentAdvice, ALinkAbsenceNamedInTheManifestIsExplained) {
     ASSERT_FALSE(a.empty());
     EXPECT_NE(a.find("fork"), std::string::npos);
     EXPECT_NE(a.find("no process image duplication"), std::string::npos);
-    EXPECT_NE(a.find("musl"), std::string::npos);
+    // THE WHOLE CLAUSE, NOT `find("musl")`. The name was interpolated from
+    // two conditionals -- an opening paren and the name -- and the closing
+    // one was never emitted, so every reader saw `(musl declares that it
+    // does not supply ...`. `find("musl")` is true of that sentence too,
+    // which is why it took a real link to notice. Assert the rendering.
+    EXPECT_NE(a.find("the C library in this graph (musl) declares"),
+              std::string::npos) << a;
+}
+
+TEST(CAbiAbsentAdvice, AnUnnamedCLibraryLeavesNoEmptyParentheses) {
+    // The other side of the same substitution: with no name there must be no
+    // parenthetical at all, rather than `graph () declares`.
+    std::vector<mcpp::targetside::CAbiAbsentEntry> absent{
+        {"fork", mcpp::targetside::CAbiAbsentForm::Link, ""},
+    };
+    auto a = mcpp::build::c_abi_absent_facility_advice(
+        "ld.lld: error: undefined symbol: fork\n", "", absent);
+    ASSERT_FALSE(a.empty());
+    EXPECT_NE(a.find("the C library in this graph declares"),
+              std::string::npos) << a;
+    EXPECT_EQ(a.find("()"), std::string::npos) << a;
 }
 
 TEST(CAbiAbsentAdvice, TheGnuSpellingIsMatchedToo) {