feat(gen): emit config.status/config.log/config.h

src/gen/config.c

@@ -0,0 +1,280 @@
+/*
+ * config.c - config.log / config.h / config.status emitters (todo 17).
+ *
+ * Four pure emitters; see gen/config.h for the model, the emitted text of
+ * each section, the sed-quote bake-in security argument, the v1
+ * limitations and the error categories.
+ *
+ * Copyright (c) 2026 huntedbytheirs
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "gen/config.h"
+
+#include "cli.h" /* STUPIDTOOLS_VERSION (the created-by / generated-by line) */
+
+#include "error.h"
+#include "gen/sh_emit.h"
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* ---- small helpers ----------------------------------------------------- */
+
+/* True when `s` is a valid POSIX shell identifier (the have_<name> /
+ * HAVE_<NAME> interpolation positions demand it; mirrors configure.c). */
+static bool
+valid_ident(const char *s)
+{
+    const unsigned char *p;
+
+    if (s == NULL || *s == '\0') {
+        return false;
+    }
+    p = (const unsigned char *)s;
+    if (!((*p >= 'a' && *p <= 'z') || (*p >= 'A' && *p <= 'Z') ||
+          *p == '_')) {
+        return false;
+    }
+    for (p++; *p != '\0'; p++) {
+        if (!((*p >= 'a' && *p <= 'z') || (*p >= 'A' && *p <= 'Z') ||
+              (*p >= '0' && *p <= '9') || *p == '_')) {
+            return false;
+        }
+    }
+    return true;
+}
+
+/* Uppercase copy of a validated identifier: "pthread" -> "PTHREAD". */
+static char *
+ident_upper(const char *s)
+{
+    size_t i;
+    size_t n = strlen(s);
+    char *up = malloc(n + 1);
+
+    if (up == NULL) {
+        return NULL;
+    }
+    for (i = 0; i < n; i++) {
+        unsigned char c = (unsigned char)s[i];
+
+        up[i] = (char)((c >= 'a' && c <= 'z') ? c - 'a' + 'A' : c);
+    }
+    up[n] = '\0';
+    return up;
+}
+
+/* ---- fixed shell text (emitted verbatim via st_sh_emit_str) ------------ */
+
+/* Section A: config.log init + original-args capture. Runs right after
+ * the preamble. The `%` in `printf 'configure invocation: %s\n'` is why
+ * this is emitted verbatim (fprintf would eat it). The two sed pipelines
+ * rewrite every ' into '\'' so the values can later be baked into
+ * config.status as single-quoted literals. */
+static const char CONFIG_LOG_INIT[] =
+    "\n"
+    "# --- config.log: transcript of this configure run ---\n"
+    "# Probe snippets append their compiler stdout/stderr to $config_log\n"
+    "# (see the probe section below); a `## results` summary of every\n"
+    "# have_<feature> value is appended after probing. The original\n"
+    "# invocation is captured here for config.status (written at the end\n"
+    "# of this script), which re-runs configure with these arguments.\n"
+    "st_orig_args=\"$@\"\n"
+    "st_configure_path=$0\n"
+    "# Single-quote-escaped copies (every ' becomes '\\'' in shell): the\n"
+    "# values can then be baked into config.status as safe quoted\n"
+    "# literals - nothing in them is ever re-expanded when config.status\n"
+    "# runs.\n"
+    "st_orig_args_q=$(printf '%s' \"$st_orig_args\" | sed \"s/'/'\\\\\\\\''/g\")\n"
+    "st_configure_path_q=$(printf '%s' \"$st_configure_path\" | sed \"s/'/'\\\\\\\\''/g\")\n"
+    ": \"${config_log:=./config.log}\"\n"
+    "{\n"
+    "    printf '%s\\n' 'This file contains any messages produced by compilers while'\n"
+    "    printf '%s\\n' 'running configure, to aid debugging if configure makes a mistake.'\n"
+    "    printf '%s\\n' ''\n"
+    "    printf '%s\\n' 'It was created by stupidtools configure "
+    STUPIDTOOLS_VERSION
+    ".'\n"
+    "    printf 'configure invocation: %s\\n' \"$st_orig_args\"\n"
+    "    printf '%s\\n' \"timestamp: $(date)\"\n"
+    "    printf '%s\\n' \"host: $(uname -s) $(uname -m)\"\n"
+    "    printf '%s\\n' \"shell: ${SHELL:-unknown}\"\n"
+    "    printf '%s\\n' ''\n"
+    "} > \"$config_log\"\n";
+
+/* Section B (part 1): the `## results` summary appended to $config_log. */
+static const char RESULTS_PRE[] =
+    "\n"
+    "# --- probe results (appended to config.log) ---\n"
+    "# One have_<feature>=yes|no line per feature, as determined by the\n"
+    "# probes above. config.log is therefore: the header (top), every\n"
+    "# probe's compiler output (middle), this summary (end).\n"
+    "{\n"
+    "    printf '%s\\n' '## results'\n";
+
+static const char RESULTS_POST[] =
+    "} >> \"$config_log\"\n";
+
+/* Section B (part 2): the ./config.h writer. */
+static const char CONFIG_H_PRE[] =
+    "\n"
+    "# --- config.h ---\n"
+    "# HAVE_<FEATURE> defines written at CONFIGURE time: one define per\n"
+    "# feature whose probe result was 'yes' (the content reflects the\n"
+    "# actual probe results, never the generator's guesses). The\n"
+    "# ST_CONFIG_H guard keeps the file safe to include repeatedly.\n"
+    "{\n"
+    "    printf '%s\\n' '/* config.h - generated by stupidtools configure "
+    STUPIDTOOLS_VERSION
+    " - DO NOT EDIT. */'\n"
+    "    printf '%s\\n' '#ifndef ST_CONFIG_H'\n"
+    "    printf '%s\\n' '#define ST_CONFIG_H'\n"
+    "    printf '%s\\n' ''\n";
+
+static const char CONFIG_H_POST[] =
+    "    printf '%s\\n' ''\n"
+    "    printf '%s\\n' '#endif /* ST_CONFIG_H */'\n"
+    "} > ./config.h\n";
+
+/* Section C: the ./config.status writer. The here-document is UNQUOTED on
+ * purpose: configure-time expansion bakes $st_orig_args_q /
+ * $st_configure_path_q into the file (expansion results are never
+ * re-parsed, so nothing can execute), while every `\$` survives as a
+ * literal `$` for config.status to expand when IT runs. */
+static const char CONFIG_STATUS[] =
+    "\n"
+    "# --- config.status ---\n"
+    "# A self-contained POSIX-sh helper written at configure time. It\n"
+    "# re-runs ./configure with the arguments of the ORIGINAL invocation\n"
+    "# (captured at the top of this script and baked in here as quoted\n"
+    "# literals, so no value is ever re-expanded when config.status\n"
+    "# runs).\n"
+    "cat > ./config.status <<ST_STATUS_EOF\n"
+    "#!/bin/sh\n"
+    "# config.status - re-runs ./configure with the original arguments.\n"
+    "# Generated by stupidtools configure "
+    STUPIDTOOLS_VERSION
+    " - DO NOT EDIT.\n"
+    "\n"
+    "st_orig_args='$st_orig_args_q'\n"
+    "st_configure_path='$st_configure_path_q'\n"
+    "\n"
+    "case \"\\${1-}\" in\n"
+    "    --recheck|'')\n"
+    "        exec \"\\${SHELL:-sh}\" \"\\$st_configure_path\" \\$st_orig_args\n"
+    "        ;;\n"
+    "    --config)\n"
+    "        printf '%s\\n' \"\\$st_orig_args\"\n"
+    "        ;;\n"
+    "    --help)\n"
+    "        printf '%s\\n' 'Usage: ./config.status [OPTION]'\n"
+    "        printf '%s\\n' 'Re-run the original ./configure invocation.'\n"
+    "        printf '%s\\n' 'Options:'\n"
+    "        printf '%s\\n' '  --recheck  re-run ./configure with the original arguments'\n"
+    "        printf '%s\\n' '  --config   print the original configure arguments'\n"
+    "        printf '%s\\n' '  --help     print this help'\n"
+    "        ;;\n"
+    "    *)\n"
+    "        printf 'config.status: error: unrecognized option %s\\n' \"\\$1\" >&2\n"
+    "        exit 1\n"
+    "        ;;\n"
+    "esac\n"
+    "ST_STATUS_EOF\n"
+    "chmod +x ./config.status\n";
+
+/* ---- the public API ---------------------------------------------------- */
+
+struct st_error *
+st_gen_config_log_init_emit(FILE *out)
+{
+    if (out == NULL) {
+        return st_error_usage("st_gen_config_log_init_emit: NULL argument");
+    }
+    if (st_sh_emit_str(out, CONFIG_LOG_INIT) < 0) {
+        return st_error_io("I/O error emitting config.log init section");
+    }
+    return NULL;
+}
+
+struct st_error *
+st_gen_config_results_emit(FILE *out, const char *const *features,
+                           size_t count)
+{
+    size_t i;
+
+    if (out == NULL || (features == NULL && count > 0)) {
+        return st_error_usage("st_gen_config_results_emit: NULL argument");
+    }
+    if (st_sh_emit_str(out, RESULTS_PRE) < 0) {
+        return st_error_io("I/O error emitting probe results section");
+    }
+    for (i = 0; i < count; i++) {
+        if (!valid_ident(features[i])) {
+            return st_error_usage("feature name is not a valid shell "
+                                  "identifier");
+        }
+        if (fprintf(out, "    printf 'have_%s=%%s\\n' \"$have_%s\"\n",
+                    features[i], features[i]) < 0) {
+            return st_error_io("I/O error emitting probe results section");
+        }
+    }
+    if (st_sh_emit_str(out, RESULTS_POST) < 0) {
+        return st_error_io("I/O error emitting probe results section");
+    }
+    return NULL;
+}
+
+struct st_error *
+st_gen_config_h_emit(FILE *out, const char *const *features, size_t count)
+{
+    size_t i;
+
+    if (out == NULL || (features == NULL && count > 0)) {
+        return st_error_usage("st_gen_config_h_emit: NULL argument");
+    }
+    if (st_sh_emit_str(out, CONFIG_H_PRE) < 0) {
+        return st_error_io("I/O error emitting config.h section");
+    }
+    for (i = 0; i < count; i++) {
+        char *up;
+
+        if (!valid_ident(features[i])) {
+            return st_error_usage("feature name is not a valid shell "
+                                  "identifier");
+        }
+        up = ident_upper(features[i]);
+        if (up == NULL) {
+            return st_error_internal("out of memory uppercasing feature "
+                                     "name");
+        }
+        if (fprintf(out,
+                    "    if [ \"$have_%s\" = \"yes\" ]; then\n"
+                    "        printf '%%s\\n' '#define HAVE_%s 1'\n"
+                    "    fi\n",
+                    features[i], up) < 0) {
+            free(up);
+            return st_error_io("I/O error emitting config.h section");
+        }
+        free(up);
+    }
+    if (st_sh_emit_str(out, CONFIG_H_POST) < 0) {
+        return st_error_io("I/O error emitting config.h section");
+    }
+    return NULL;
+}
+
+struct st_error *
+st_gen_config_status_emit(FILE *out)
+{
+    if (out == NULL) {
+        return st_error_usage("st_gen_config_status_emit: NULL argument");
+    }
+    if (st_sh_emit_str(out, CONFIG_STATUS) < 0) {
+        return st_error_io("I/O error emitting config.status section");
+    }
+    return NULL;
+}

src/gen/config.h

@@ -0,0 +1,92 @@
+/*
+ * config.h - emitters for the configure-time auxiliary artifacts
+ * (todo 17): config.log, config.h and config.status.
+ *
+ * MODEL: like everything in src/gen/, these functions are PURE CODE
+ * GENERATORS. They emit POSIX-sh sections INTO the generated ./configure;
+ * the artifacts themselves are written AT CONFIGURE TIME by the generated
+ * script, so their contents always reflect the actual probe results and
+ * the actual invocation - never the generator's guesses.
+ *
+ * THE FOUR SECTIONS (see also gen/configure.h for their placement in the
+ * generated script):
+ *
+ *  st_gen_config_log_init_emit      after the preamble: capture the
+ *      original invocation (st_orig_args="$@", st_configure_path=$0,
+ *      plus single-quote-escaped copies built with sed) and truncate-
+ *      write the transcript header (created-by line, original
+ *      arguments, timestamp, host, shell) into $config_log. $config_log
+ *      is defaulted here with `:=`, idempotently with todo 12's cache
+ *      boilerplate. Probe snippets (todo 12) append their compiler
+ *      stdout/stderr to the same file.
+ *  st_gen_config_results_emit       after the probe section: append a
+ *      `## results` block to $config_log with one
+ *      `have_<feature>=yes|no` line per top-level feature.
+ *  st_gen_config_h_emit             after the probe section: write
+ *      ./config.h with the ST_CONFIG_H guard and one
+ *      `#define HAVE_<FEATURE> 1` per feature whose have_<feature>
+ *      resolved to "yes" at configure time (the feature name upper-
+ *      cased; a failed feature gets no define).
+ *  st_gen_config_status_emit        at the very end (after Makefile
+ *      substitution, before exit 0): write ./config.status - a
+ *      standalone POSIX-sh script with the captured arguments baked in
+ *      as quoted literals (so nothing in them is ever re-expanded when
+ *      config.status runs) - and chmod +x it. Its arms: ''/--recheck ->
+ *      `exec "${SHELL:-sh}" "$st_configure_path" $st_orig_args`;
+ *      --config -> print the original args; --help -> brief usage;
+ *      anything else -> error + exit 1.
+ *
+ * SECURITY (the sed-quote bake-in): the captured args/path are rewritten
+ * with `sed "s/'/'\\''/g"` (every `'` becomes `'\''`) and stored in
+ * st_orig_args_q / st_configure_path_q. config.status assigns them as
+ * single-quoted literals (`st_orig_args='...'`), so a value containing
+ * `$(...)`, backticks, spaces or `&` is inert both when configure writes
+ * config.status (here-document expansion never re-parses expansion
+ * results) and when config.status runs (the quotes are real script text
+ * there). Proven by the injection test (todo 17, case f).
+ *
+ * KNOWN v1 LIMITATIONS (documented, deliberately simple):
+ *  - the recheck arm expands $st_orig_args UNQUOTED, so positional args
+ *    containing spaces or glob characters are not preserved through
+ *    --recheck (the v1 surface is --prefix/--host/--build);
+ *  - st_configure_path is captured verbatim ($0), so config.status must
+ *    be run from the same directory configure was run from;
+ *  - args containing literal newlines are pathological (they would break
+ *    the one-line bake-in).
+ *
+ * ERRORS: NULL arguments and feature names that are not valid POSIX shell
+ * identifiers return ST_ERR_USAGE (the names land in have_<name> and
+ * #define HAVE_<NAME> positions, which cannot be shell-quoted); stream
+ * write failures return ST_ERR_IO.
+ *
+ * Copyright (c) 2026 huntedbytheirs
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef ST_GEN_CONFIG_H
+#define ST_GEN_CONFIG_H
+
+#include <stddef.h>
+#include <stdio.h>
+
+struct st_error;
+
+/* Emit the config.log init + original-args capture section. */
+struct st_error *st_gen_config_log_init_emit(FILE *out);
+
+/* Emit the post-probe `## results` summary appended to $config_log.
+ * `features` holds the top-level feature names (validated identifiers),
+ * one emitted `have_<name>=%s` line per entry. */
+struct st_error *st_gen_config_results_emit(FILE *out,
+                                            const char *const *features,
+                                            size_t count);
+
+/* Emit the ./config.h writer (ST_CONFIG_H guard + per-feature defines). */
+struct st_error *st_gen_config_h_emit(FILE *out,
+                                      const char *const *features,
+                                      size_t count);
+
+/* Emit the ./config.status writer (+ chmod +x). */
+struct st_error *st_gen_config_status_emit(FILE *out);
+
+#endif /* ST_GEN_CONFIG_H */

src/gen/configure.c

@@ -20,6 +20,7 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
+#include "gen/config.h"
 #include "gen/configure.h"
 
 #include "cli.h" /* STUPIDTOOLS_VERSION (the generated-by version string) */
@@ -327,9 +328,7 @@ static const char SUBST_LOOKUP_TAIL[] =
     "    done < ./Makefile.in\n"
     "}\n"
     "\n"
-    "st_subst\n"
-    "\n"
-    "exit 0\n";
+    "st_subst\n";
 
 /* ---- section emitters -------------------------------------------------- */
 
@@ -570,6 +569,27 @@ done:
     return err;
 }
 
+/* Append `name` (owned) to the feature-name list, growing it as needed.
+ * Used by the probe-section loop to collect the names the todo-17 results
+ * summary + config.h defines are emitted from. */
+static struct st_error *
+collect_feature_name(char ***names, size_t *count, size_t *cap, char *name)
+{
+    if (*count == *cap) {
+        size_t ncap = *cap == 0 ? 8 : *cap * 2;
+        char **nn = realloc(*names, ncap * sizeof(*nn));
+
+        if (nn == NULL) {
+            return st_error_internal("out of memory collecting feature "
+                                     "names");
+        }
+        *names = nn;
+        *cap = ncap;
+    }
+    (*names)[(*count)++] = name;
+    return NULL;
+}
+
 /* ---- the public API ---------------------------------------------------- */
 
 struct st_error *
@@ -583,6 +603,9 @@ st_gen_configure_emit(FILE *out, const struct st_kdl_document *doc,
     const struct st_kdl_node *node;
     char **subst_names = NULL;
     size_t n_subst = 0;
+    char **feat_names = NULL;
+    size_t n_feat = 0;
+    size_t feat_cap = 0;
 
     if (out == NULL || doc == NULL || ctx == NULL) {
         return st_error_usage("st_gen_configure_emit: NULL argument");
@@ -634,7 +657,13 @@ st_gen_configure_emit(FILE *out, const struct st_kdl_document *doc,
         goto done;
     }
 
-    /* 3. host detection */
+    /* 3. config.log init + original-args capture (todo 17) */
+    err = st_gen_config_log_init_emit(out);
+    if (err != NULL) {
+        goto done;
+    }
+
+    /* 4. host detection */
     if (st_sh_emit_str(out, HOST_DETECT_PRE) < 0) {
         err = st_error_io("I/O error emitting host detection");
         goto done;
@@ -648,7 +677,7 @@ st_gen_configure_emit(FILE *out, const struct st_kdl_document *doc,
         goto done;
     }
 
-    /* 4. toolchain defaults (before the cache boilerplate; see the header) */
+    /* 5. toolchain defaults (before the cache boilerplate; see the header) */
     if (st_sh_emit_str(out, TOOLCHAIN_DEFAULTS_PRE) < 0) {
         err = st_error_io("I/O error emitting toolchain defaults");
         goto done;
@@ -681,15 +710,18 @@ st_gen_configure_emit(FILE *out, const struct st_kdl_document *doc,
         goto done;
     }
 
-    /* 5. cache boilerplate (todo 12) */
+    /* 6. cache boilerplate (todo 12) */
     err = st_probe_emit_cache_functions(out);
     if (err != NULL) {
         goto done;
     }
 
-    /* 6. probe section: each top-level `feature` node in document order */
+    /* 7. probe section: each top-level `feature` node in document order.
+     * The resolved feature names are collected here for the todo-17
+     * results summary + config.h defines, emitted right after the loop. */
     for (node = doc->nodes; node != NULL; node = node->next) {
         bool is_feature = false;
+        char *fname = NULL;
 
         err = name_equals(&node->name, "feature", &is_feature);
         if (err != NULL) {
@@ -702,21 +734,59 @@ st_gen_configure_emit(FILE *out, const struct st_kdl_document *doc,
         if (err != NULL) {
             goto done;
         }
+        /* a successful emit_feature guarantees the name is a valid shell
+         * identifier (it errors otherwise), so the have_<name> /
+         * HAVE_<NAME> interpolation below is safe */
+        err = extract_string(&node->args->value, "feature name", &fname);
+        if (err != NULL) {
+            goto done;
+        }
+        err = collect_feature_name(&feat_names, &n_feat, &feat_cap, fname);
+        if (err != NULL) {
+            free(fname);
+            goto done;
+        }
     }
 
-    /* 7. substitution section */
+    /* 8. probe-results summary + config.h (todo 17) */
+    err = st_gen_config_results_emit(out, (const char *const *)feat_names,
+                                     n_feat);
+    if (err != NULL) {
+        goto done;
+    }
+    err = st_gen_config_h_emit(out, (const char *const *)feat_names, n_feat);
+    if (err != NULL) {
+        goto done;
+    }
+
+    /* 9. substitution section */
     err = emit_subst_lookup(out, (const char *const *)subst_names, n_subst);
     if (err != NULL) {
         goto done;
     }
 
-    /* 8. exit 0 is already the last line of the substitution tail */
+    /* 10. config.status (todo 17): written after substitution, before the
+     * final exit 0 */
+    err = st_gen_config_status_emit(out);
+    if (err != NULL) {
+        goto done;
+    }
+    if (st_sh_emit_str(out, "\nexit 0\n") < 0) {
+        err = st_error_io("I/O error emitting configure");
+        goto done;
+    }
+
+    /* 11. final stream check */
     if (ferror(out)) {
         err = st_error_io("I/O error emitting configure");
         goto done;
     }
 
 done:
+    for (i = 0; i < n_feat; i++) {
+        free(feat_names[i]);
+    }
+    free(feat_names);
     free(subst_names);
     return err;
 }

src/gen/configure.h

@@ -12,7 +12,7 @@
  * -------------------------------------------------------------
  *  1. `#!/bin/sh` + a header comment (generated-by, version).
  *  2. PREAMBLE — v1 MINIMAL argument handling, structurally marked with a
- *     `# === preamble ===` comment so todo 18 replaces it whole:
+ *     `# --- PREAMBLE ---` comment so todo 18 replaces it whole:
  *       - `--prefix=<dir>` stores $prefix (default /usr/local);
  *       - `--host=<triplet>` / `--build=<triplet>` store $host / $build;
  *         $cross_compiling=yes when --host differs from --build (a simple
@@ -22,16 +22,23 @@
  *         the positional form is accepted-but-ignored until todo 18;
  *       - an unknown `--*` prints "unrecognized option" to stderr and
  *         exits 1.
- *  3. HOST DETECTION: `st_os=$(uname -s)`, then the st_os_norm() emitted by
+ *  3. CONFIG.LOG INIT (todo 17) — capture the original invocation
+ *     (st_orig_args="$@", st_configure_path=$0, plus single-quote-escaped
+ *     copies built with sed for the config.status bake-in) and
+ *     truncate-write the transcript header (created-by line, original
+ *     arguments, timestamp, host, shell) into $config_log (defaulted here
+ *     with `:=`, idempotently with todo 12's boilerplate default). Probe
+ *     snippets append their compiler stdout/stderr to the same file.
+ *  4. HOST DETECTION: `st_os=$(uname -s)`, then the st_os_norm() emitted by
  *     resolve.h's st_resolve_emit_os_norm() rewrites it in place; `st_cc_id
  *     =unknown` (v1, no compiler-id sniffing at configure time).
- *  4. TOOLCHAIN DEFAULTS: for each registered var name (CC/CFLAGS/...) emit
+ *  5. TOOLCHAIN DEFAULTS: for each registered var name (CC/CFLAGS/...) emit
  *     `VAR="${VAR:-<default>}"` where <default> is the registry VALUE at
  *     generation time (st_sh_quote'd; typically empty for CFLAGS), then
  *     `LIBS=""`. Emitted BEFORE the probe cache boilerplate because that
  *     boilerplate uses `:=` fallbacks that must not clobber these values.
- *  5. CACHE BOILERPLATE: probe.h's st_probe_emit_cache_functions (todo 12).
- *  6. PROBE SECTION: for each top-level `feature` node in document order,
+ *  6. CACHE BOILERPLATE: probe.h's st_probe_emit_cache_functions (todo 12).
+ *  7. PROBE SECTION: for each top-level `feature` node in document order,
  *     for each check child, derive the checkname via resolve.h's
  *     st_resolve_check_name, build the probe via checks.h's
  *     st_check_probe_build, and emit the snippet via probe.h's
@@ -42,14 +49,31 @@
  *     v1 pkg-config guard `if command -v pkg-config >/dev/null 2>&1; then
  *     ... LIBS="$LIBS $(pkg-config --libs 'X')" ...; fi`. Generic over the
  *     check kinds, never hardcoded per feature name.
- *  7. SUBSTITUTION: reads ./Makefile.in (cwd, the v1 source-dir contract)
+ *  8. PROBE RESULTS + CONFIG.H (todo 17) — append a `## results` block to
+ *     $config_log (one `have_<feature>=yes|no` line per top-level feature),
+ *     then write ./config.h with the ST_CONFIG_H guard and one
+ *     `#define HAVE_<FEATURE> 1` per feature whose have_<feature> resolved
+ *     to "yes". Both reflect the configure-time probe results, never
+ *     generation-time guesses; feature names are validated identifiers
+ *     (see ERRORS), so the have_<name> / HAVE_<NAME> interpolation is
+ *     safe.
+ *  9. SUBSTITUTION: reads ./Makefile.in (cwd, the v1 source-dir contract)
  *     and replaces every `@VAR@` (VAR = registered vars ∪ {LIBS, prefix,
  *     srcdir}) with the shell variable's value, writing ./Makefile. An
  *     UNRESOLVED `@SOMETHING@` is a CONFIGURE-TIME error naming the
  *     variable (the generator cannot know the user's Makefile.in), reported
  *     after substitution via the per-line lookup; a missing Makefile.in is
  *     a clean error. See the SUBSTITUTION approach note below.
- *  8. `exit 0`.
+ * 10. CONFIG.STATUS (todo 17) — write ./config.status (a standalone
+ *     POSIX-sh script with the original arguments baked in as quoted
+ *     literals, so nothing in them is ever re-expanded when it runs) and
+ *     chmod +x it. Arms: ''/--recheck -> `exec "${SHELL:-sh}"
+ *     "$st_configure_path" $st_orig_args`; --config -> print the original
+ *     args; --help -> brief usage; unknown -> error + exit 1. v1
+ *     limitations (documented in gen/config.h): positional args with
+ *     spaces/globs are not preserved by the unquoted recheck expansion;
+ *     config.status must run from the same directory as configure.
+ * 11. `exit 0`.
  *
  * SUBSTITUTION APPROACH (documented because the plan flagged it)
  * --------------------------------------------------------------

tests/unit/test_gen_configure.c

@@ -1,4 +1,4 @@
-/* LINK: ../../src/gen/configure.c ../../src/gen/sh_emit.c ../../src/detect/probe.c ../../src/detect/checks.c ../../src/detect/check_registry.c ../../src/detect/resolve.c ../../src/kdl/schema.c ../../src/kdl/parser.c ../../src/kdl/lexer.c ../../src/kdl/value.c ../../src/ext/abi.c ../../src/ext/lang_c.c ../../src/ext/lang_cpp.c ../../src/error.c ../../src/span.c */
+/* LINK: ../../src/gen/config.c ../../src/gen/configure.c ../../src/gen/sh_emit.c ../../src/detect/probe.c ../../src/detect/checks.c ../../src/detect/check_registry.c ../../src/detect/resolve.c ../../src/kdl/schema.c ../../src/kdl/parser.c ../../src/kdl/lexer.c ../../src/kdl/value.c ../../src/ext/abi.c ../../src/ext/lang_c.c ../../src/ext/lang_cpp.c ../../src/error.c ../../src/span.c */
 #ifndef _POSIX_C_SOURCE
 #define _POSIX_C_SOURCE 200809L /* mkdtemp/unsetenv/setenv (POSIX.1-2008) */
 #endif
@@ -200,6 +200,90 @@ syntax_check(const char *shell, const char *path)
     return WEXITSTATUS(spawned);
 }
 
+/* Run "./config.status <args>" with cwd = temp_dir; stdout to status.out,
+ * stderr to status.err. Returns the exit status, or -1 if not spawned. */
+static int
+run_status(const char *args)
+{
+    char cmd[2400];
+    int n;
+    int spawned;
+
+    n = snprintf(cmd, sizeof cmd,
+                 "cd '%s' && ./config.status %s >'%s/status.out' "
+                 "2>'%s/status.err'",
+                 temp_dir, args != NULL ? args : "", temp_dir, temp_dir);
+    if (n < 0 || (size_t)n >= sizeof cmd) {
+        return -1;
+    }
+    spawned = system(cmd);
+    if (spawned == -1) {
+        return -1;
+    }
+    return WEXITSTATUS(spawned);
+}
+
+/* Slurp temp_dir/<name>, or NULL. Caller frees. */
+static char *
+slurp_named(const char *name)
+{
+    char path[600];
+
+    if (mkpath(path, sizeof path, name) < 0) {
+        return NULL;
+    }
+    return slurp(path);
+}
+
+/* Remove temp_dir/<name> (a missing file is not an error: the stale_state
+ * checks remove outputs that may or may not exist). Returns 0 on success. */
+static int
+remove_named(const char *name)
+{
+    char path[600];
+
+    if (mkpath(path, sizeof path, name) < 0) {
+        return -1;
+    }
+    (void)remove(path);
+    return 0;
+}
+
+/* Parse + validate + emit an INLINE document into temp_dir/configure. */
+static int
+emit_inline_configure(struct st_ext_ctx *ctx, const char *docsrc)
+{
+    struct st_kdl_document *doc = NULL;
+    struct st_error *err = NULL;
+    char conf[600];
+
+    doc = st_kdl_parse(docsrc, "inline.kdl", &err);
+    if (err != NULL) {
+        st_error_free(err);
+        return -1;
+    }
+    if (doc == NULL) {
+        return -1;
+    }
+    err = st_kdl_validate(doc);
+    if (err != NULL) {
+        st_error_free(err);
+        st_kdl_document_free(doc);
+        return -1;
+    }
+    if (mkpath(conf, sizeof conf, "configure") < 0) {
+        st_kdl_document_free(doc);
+        return -1;
+    }
+    err = st_gen_configure_emit_path(conf, doc, ctx);
+    st_kdl_document_free(doc);
+    if (err != NULL) {
+        st_error_free(err);
+        return -1;
+    }
+    return 0;
+}
+
 /* ---- fixture loading (same as test_schema.c) -------------------------- */
 
 static const char *
@@ -618,6 +702,272 @@ test_cross_compile(const MunitParameter params[], void *data)
     return MUNIT_OK;
 }
 
+/* ---- todo 17 (a): the three new sections stay shell-safe ------------- */
+
+static MunitResult
+test_config_sections_syntax(const MunitParameter params[], void *data)
+{
+    (void)params;
+    (void)data;
+    struct st_ext_ctx *ctx;
+    char conf[600];
+    char *bytes;
+
+    ctx = build_ctx();
+    munit_assert_not_null(ctx);
+    munit_assert_int(emit_fixture_configure(ctx), ==, 0);
+    st_ext_ctx_free(ctx);
+
+    munit_assert_int(mkpath(conf, sizeof conf, "configure"), >, 0);
+    munit_assert_int(syntax_check("sh", conf), ==, 0);
+    munit_assert_int(syntax_check("bash", conf), ==, 0);
+    munit_assert_int(syntax_check("zsh", conf), ==, 0);
+
+    bytes = slurp(conf);
+    munit_assert_not_null(bytes);
+    /* the three sections are structurally marked (--- not ===, per the
+     * F3 banned-construct grep) */
+    munit_assert_not_null(strstr(bytes, "# --- config.log:"));
+    munit_assert_not_null(strstr(bytes, "# --- config.h ---"));
+    munit_assert_not_null(strstr(bytes, "# --- config.status ---"));
+    munit_assert_not_null(strstr(bytes, "'## results'"));
+    free(bytes);
+    return MUNIT_OK;
+}
+
+/* ---- todo 17 (b): a real run writes config.h/config.log/config.status -- */
+
+static MunitResult
+test_config_artifacts(const MunitParameter params[], void *data)
+{
+    (void)params;
+    (void)data;
+    struct st_ext_ctx *ctx;
+    char status[600];
+    char *ch;
+    char *cl;
+
+    ctx = build_ctx();
+    munit_assert_not_null(ctx);
+    munit_assert_int(emit_fixture_configure(ctx), ==, 0);
+    st_ext_ctx_free(ctx);
+
+    munit_assert_int(write_makefile_in(STD_MAKEFILE_IN), ==, 0);
+    munit_assert_int(run_configure(NULL), ==, 0);
+
+    /* config.h: the ST_CONFIG_H guard + one define per resolved feature
+     * (content asserted, not mere existence) */
+    ch = slurp_named("config.h");
+    munit_assert_not_null(ch);
+    munit_assert_not_null(strstr(ch, "#ifndef ST_CONFIG_H"));
+    munit_assert_not_null(strstr(ch, "#define ST_CONFIG_H"));
+    munit_assert_not_null(strstr(ch, "#define HAVE_PTHREAD 1"));
+    munit_assert_not_null(strstr(ch, "#define HAVE_MATH 1"));
+    free(ch);
+
+    /* config.log: the transcript header + the ## results summary */
+    cl = slurp_named("config.log");
+    munit_assert_not_null(cl);
+    munit_assert_not_null(
+        strstr(cl, "It was created by stupidtools configure"));
+    munit_assert_not_null(strstr(cl, "## results"));
+    munit_assert_not_null(strstr(cl, "have_pthread=yes"));
+    munit_assert_not_null(strstr(cl, "have_math=yes"));
+    free(cl);
+
+    /* config.status: exists, is executable, and is valid POSIX-sh */
+    munit_assert_int(mkpath(status, sizeof status, "config.status"), >, 0);
+    munit_assert_int(access(status, F_OK), ==, 0);
+    munit_assert_int(access(status, X_OK), ==, 0);
+    munit_assert_int(syntax_check("sh", status), ==, 0);
+    munit_assert_int(syntax_check("bash", status), ==, 0);
+    munit_assert_int(syntax_check("zsh", status), ==, 0);
+    return MUNIT_OK;
+}
+
+/* ---- todo 17 (c): config.status --config prints the original args ----- */
+
+static MunitResult
+test_config_status_config(const MunitParameter params[], void *data)
+{
+    (void)params;
+    (void)data;
+    struct st_ext_ctx *ctx;
+    char *out;
+
+    ctx = build_ctx();
+    munit_assert_not_null(ctx);
+    munit_assert_int(emit_fixture_configure(ctx), ==, 0);
+    st_ext_ctx_free(ctx);
+
+    munit_assert_int(write_makefile_in(STD_MAKEFILE_IN), ==, 0);
+    munit_assert_int(run_configure("--prefix=/opt/x"), ==, 0);
+    munit_assert_int(run_status("--config"), ==, 0);
+
+    out = slurp_named("status.out");
+    munit_assert_not_null(out);
+    munit_assert_string_equal(out, "--prefix=/opt/x\n");
+    free(out);
+    return MUNIT_OK;
+}
+
+/* ---- todo 17 (d): config.status --recheck re-runs configure ----------- */
+
+static MunitResult
+test_config_status_recheck(const MunitParameter params[], void *data)
+{
+    (void)params;
+    (void)data;
+    struct st_ext_ctx *ctx;
+    char *mk;
+    char *ch;
+
+    ctx = build_ctx();
+    munit_assert_not_null(ctx);
+    munit_assert_int(emit_fixture_configure(ctx), ==, 0);
+    st_ext_ctx_free(ctx);
+
+    munit_assert_int(write_makefile_in(STD_MAKEFILE_IN), ==, 0);
+    munit_assert_int(run_configure("--prefix=/opt/x"), ==, 0);
+
+    /* stale_state: destroy the outputs, then --recheck regenerates them
+     * (observable regeneration, not a cached no-op) */
+    munit_assert_int(remove_named("Makefile"), ==, 0);
+    munit_assert_int(remove_named("config.h"), ==, 0);
+    munit_assert_int(run_status("--recheck"), ==, 0);
+
+    mk = makefile_text();
+    munit_assert_not_null(mk);
+    munit_assert_not_null(strstr(mk, "prefix = /opt/x"));
+    free(mk);
+
+    ch = slurp_named("config.h");
+    munit_assert_not_null(ch);
+    munit_assert_not_null(strstr(ch, "#define HAVE_PTHREAD 1"));
+    free(ch);
+    return MUNIT_OK;
+}
+
+/* ---- todo 17 (e): a failed feature gets no HAVE_ define --------------- */
+
+static MunitResult
+test_config_failed_feature(const MunitParameter params[], void *data)
+{
+    (void)params;
+    (void)data;
+    static const char *const docsrc =
+        "project \"x\" version \"1.0\"\n"
+        "feature \"nope\" { header \"nope_missing_xyz.h\" }\n"
+        "feature \"ok\" { header \"unistd.h\" }\n";
+    struct st_ext_ctx *ctx;
+    char *ch;
+    char *cl;
+
+    ctx = build_ctx();
+    munit_assert_not_null(ctx);
+    munit_assert_int(emit_inline_configure(ctx, docsrc), ==, 0);
+    st_ext_ctx_free(ctx);
+
+    munit_assert_int(write_makefile_in("CC = @CC@\n"), ==, 0);
+    munit_assert_int(run_configure(NULL), ==, 0);
+
+    ch = slurp_named("config.h");
+    munit_assert_not_null(ch);
+    munit_assert_null(strstr(ch, "HAVE_NOPE"));
+    munit_assert_not_null(strstr(ch, "#define HAVE_OK 1"));
+    free(ch);
+
+    cl = slurp_named("config.log");
+    munit_assert_not_null(cl);
+    munit_assert_not_null(strstr(cl, "have_nope=no"));
+    munit_assert_not_null(strstr(cl, "have_ok=yes"));
+    free(cl);
+    return MUNIT_OK;
+}
+
+/* ---- todo 17 (f): injected values never execute ----------------------- */
+
+static MunitResult
+test_config_status_injection(const MunitParameter params[], void *data)
+{
+    (void)params;
+    (void)data;
+    struct st_ext_ctx *ctx;
+    char pwned1[600];
+    char pwned2[600];
+    char *mk;
+
+    ctx = build_ctx();
+    munit_assert_not_null(ctx);
+    munit_assert_int(emit_fixture_configure(ctx), ==, 0);
+    st_ext_ctx_free(ctx);
+
+    munit_assert_int(mkpath(pwned1, sizeof pwned1, "pwned1"), >, 0);
+    munit_assert_int(mkpath(pwned2, sizeof pwned2, "pwned2"), >, 0);
+    munit_assert_int(write_makefile_in("prefix = @prefix@\n"), ==, 0);
+
+    /* The payloads use ${IFS} instead of a literal space: they contain no
+     * whitespace, so they survive the (documented, v1) unquoted recheck
+     * expansion as one word - yet they would create the marker files if
+     * any shell ever executed them. */
+    munit_assert_int(run_configure("--prefix='$(touch${IFS}pwned1)'"), ==, 0);
+    munit_assert_int(access(pwned1, F_OK), ==, -1);
+    munit_assert_int(run_status("--config"), ==, 0);
+    munit_assert_int(access(pwned1, F_OK), ==, -1);
+    munit_assert_int(run_status("--recheck"), ==, 0);
+    munit_assert_int(access(pwned1, F_OK), ==, -1);
+    mk = makefile_text();
+    munit_assert_not_null(mk);
+    munit_assert_not_null(strstr(mk, "prefix = $(touch${IFS}pwned1)"));
+    free(mk);
+
+    /* payload 2: backticks - same guarantee, via a fresh configure run */
+    munit_assert_int(run_configure("--prefix='`touch${IFS}pwned2`'"), ==, 0);
+    munit_assert_int(access(pwned2, F_OK), ==, -1);
+    munit_assert_int(run_status("--config"), ==, 0);
+    munit_assert_int(access(pwned2, F_OK), ==, -1);
+    munit_assert_int(run_status("--recheck"), ==, 0);
+    munit_assert_int(access(pwned2, F_OK), ==, -1);
+    mk = makefile_text();
+    munit_assert_not_null(mk);
+    munit_assert_not_null(strstr(mk, "prefix = `touch${IFS}pwned2`"));
+    free(mk);
+    return MUNIT_OK;
+}
+
+/* ---- todo 17 (g): config.status --help and unknown-option handling ---- */
+
+static MunitResult
+test_config_status_help(const MunitParameter params[], void *data)
+{
+    (void)params;
+    (void)data;
+    struct st_ext_ctx *ctx;
+    char *out;
+    char *e;
+
+    ctx = build_ctx();
+    munit_assert_not_null(ctx);
+    munit_assert_int(emit_fixture_configure(ctx), ==, 0);
+    st_ext_ctx_free(ctx);
+
+    munit_assert_int(write_makefile_in(STD_MAKEFILE_IN), ==, 0);
+    munit_assert_int(run_configure(NULL), ==, 0);
+
+    munit_assert_int(run_status("--help"), ==, 0);
+    out = slurp_named("status.out");
+    munit_assert_not_null(out);
+    munit_assert_not_null(strstr(out, "Usage"));
+    free(out);
+
+    munit_assert_int(run_status("--bogus"), !=, 0);
+    e = slurp_named("status.err");
+    munit_assert_not_null(e);
+    munit_assert_not_null(strstr(e, "unrecognized option"));
+    free(e);
+    return MUNIT_OK;
+}
+
 static MunitTest tests[] = {
     { "/gen/syntax", test_syntax, setup, teardown, MUNIT_TEST_OPTION_NONE,
       NULL },
@@ -639,6 +989,20 @@ static MunitTest tests[] = {
       teardown, MUNIT_TEST_OPTION_NONE, NULL },
     { "/gen/cross-compile", test_cross_compile, setup, teardown,
       MUNIT_TEST_OPTION_NONE, NULL },
+    { "/gen/config-sections-syntax", test_config_sections_syntax, setup,
+      teardown, MUNIT_TEST_OPTION_NONE, NULL },
+    { "/gen/config-artifacts", test_config_artifacts, setup, teardown,
+      MUNIT_TEST_OPTION_NONE, NULL },
+    { "/gen/config-status-config", test_config_status_config, setup,
+      teardown, MUNIT_TEST_OPTION_NONE, NULL },
+    { "/gen/config-status-recheck", test_config_status_recheck, setup,
+      teardown, MUNIT_TEST_OPTION_NONE, NULL },
+    { "/gen/config-failed-feature", test_config_failed_feature, setup,
+      teardown, MUNIT_TEST_OPTION_NONE, NULL },
+    { "/gen/config-status-injection", test_config_status_injection, setup,
+      teardown, MUNIT_TEST_OPTION_NONE, NULL },
+    { "/gen/config-status-help", test_config_status_help, setup, teardown,
+      MUNIT_TEST_OPTION_NONE, NULL },
     { NULL, NULL, NULL, NULL, MUNIT_TEST_OPTION_NONE, NULL },
 };