Derive err_maxval's code set from the header, not a hardcoded list

The previous err_maxval hardcoded the list of AKERR_* codes, which silently
rots the moment a code is added. Instead, parse the generated akerror.h at
runtime: discover every "#define AKERR_<NAME> (AKERR_LAST_ERRNO_VALUE + N)",
take the highest offset actually defined, and assert AKERR_MAX_ERR_VALUE covers
it. A compile-time cross-check ties the parsed ceiling to the compiled macro so
the test can't pass by reading a stale header.

CMake injects the header path as AKERR_GENERATED_HEADER. Verified: the test
fails (max_err_value >= highest_code) when pointed at a +15 header while
AKERR_BADEXC is +17, and now also strengthens header mutation coverage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CMakeLists.txt

@@ -81,6 +81,11 @@ foreach(_test IN LISTS AKERR_TESTS)
     add_test(NAME ${_test} COMMAND test_${_test})
 endforeach()
 
+# err_maxval parses the generated header to check AKERR_MAX_ERR_VALUE covers
+# every AKERR_* code, so it needs the path to the header it was built against.
+target_compile_definitions(test_err_maxval PRIVATE
+    AKERR_GENERATED_HEADER="${GENERATED_AKERROR_H}")
+
 set_tests_properties(
     ${AKERR_WILL_FAIL_TESTS}
     PROPERTIES WILL_FAIL TRUE

tests/err_maxval.c

@@ -1,52 +1,92 @@
 #include "akerror.h"
 #include "err_capture.h"
+#include <regex.h>
 
 /*
  * AKERR_MAX_ERR_VALUE sizes the __AKERR_ERROR_NAMES table and is the upper bound
- * akerr_name_for_status() will accept. If it is smaller than the highest AKERR_*
+ * akerr_name_for_status() accepts. If it is smaller than the highest AKERR_*
  * code, those codes silently lose their names (this was a real bug: the max was
  * +15 while AKERR_BADEXC is +17).
  *
- * Guard the invariant: the AKERR_* range reserved above AKERR_LAST_ERRNO_VALUE
- * must be larger than the number of AKERR_* codes defined, and every code must
- * be individually indexable.
+ * Rather than hardcode the list of codes (which rots the moment someone adds a
+ * code), this test parses the generated akerror.h, discovers every
+ *     #define AKERR_<NAME> (AKERR_LAST_ERRNO_VALUE + <N>)
+ * finds the highest offset actually defined, and verifies AKERR_MAX_ERR_VALUE
+ * covers it. The path to the header the library was built from is injected by
+ * CMake as AKERR_GENERATED_HEADER.
  */
 
-/* Every AKERR_* library error code. Keep in sync with akerror.h. */
-static const int akerr_codes[] = {
-    AKERR_NULLPOINTER,
-    AKERR_OUTOFBOUNDS,
-    AKERR_API,
-    AKERR_ATTRIBUTE,
-    AKERR_TYPE,
-    AKERR_KEY,
-    AKERR_INDEX,
-    AKERR_FORMAT,
-    AKERR_IO,
-    AKERR_VALUE,
-    AKERR_RELATIONSHIP,
-    AKERR_EOF,
-    AKERR_CIRCULAR_REFERENCE,
-    AKERR_ITERATOR_BREAK,
-    AKERR_NOT_IMPLEMENTED,
-    AKERR_BADEXC,
-};
+#ifndef AKERR_GENERATED_HEADER
+#error "AKERR_GENERATED_HEADER (path to generated akerror.h) must be defined"
+#endif
 
 int main(void)
 {
-    int n = (int)(sizeof(akerr_codes) / sizeof(akerr_codes[0]));
+    FILE *fh = fopen(AKERR_GENERATED_HEADER, "r");
+    AKERR_CHECK(fh != NULL);
 
-    /* AKERR_MAX_ERR_VALUE must reserve more codes than are actually defined. */
-    AKERR_CHECK((AKERR_MAX_ERR_VALUE - AKERR_LAST_ERRNO_VALUE) > n);
+    /*  #define  AKERR_NAME   (AKERR_LAST_ERRNO_VALUE + N)   */
+    regex_t re;
+    const char *pattern =
+	"^[[:space:]]*#define[[:space:]]+(AKERR_[A-Za-z0-9_]+)[[:space:]]+"
+	"\\(AKERR_LAST_ERRNO_VALUE[[:space:]]*\\+[[:space:]]*([0-9]+)\\)";
+    AKERR_CHECK(regcomp(&re, pattern, REG_EXTENDED) == 0);
 
-    /* Stronger: every defined code must fall within the addressable range so
-     * its name can be stored and retrieved. */
-    for ( int i = 0; i < n; i++ ) {
-        AKERR_CHECK(akerr_codes[i] > AKERR_LAST_ERRNO_VALUE);
-        AKERR_CHECK(akerr_codes[i] <= AKERR_MAX_ERR_VALUE);
+    int highest_code = -1;          /* highest offset among real error codes */
+    char highest_name[64] = "";
+    int max_err_value = -1;         /* offset parsed from AKERR_MAX_ERR_VALUE  */
+    int code_count = 0;
+
+    char line[4096];
+    regmatch_t m[3];
+    while ( fgets(line, sizeof(line), fh) != NULL ) {
+	if ( regexec(&re, line, 3, m, 0) != 0 ) {
+	    continue;
+	}
+
+	char name[64];
+	int nlen = (int)(m[1].rm_eo - m[1].rm_so);
+	if ( nlen >= (int)sizeof(name) ) {
+	    nlen = (int)sizeof(name) - 1;
+	}
+	memcpy(name, line + m[1].rm_so, nlen);
+	name[nlen] = '\0';
+
+	char num[16];
+	int vlen = (int)(m[2].rm_eo - m[2].rm_so);
+	if ( vlen >= (int)sizeof(num) ) {
+	    vlen = (int)sizeof(num) - 1;
+	}
+	memcpy(num, line + m[2].rm_so, vlen);
+	num[vlen] = '\0';
+	int offset = atoi(num);
+
+	if ( strcmp(name, "AKERR_MAX_ERR_VALUE") == 0 ) {
+	    max_err_value = offset;
+	} else {
+	    code_count++;
+	    if ( offset > highest_code ) {
+		highest_code = offset;
+		snprintf(highest_name, sizeof(highest_name), "%s", name);
+	    }
+	}
     }
+    regfree(&re);
+    fclose(fh);
 
-    fprintf(stderr, "err_maxval ok (%d codes, range %d)\n",
-	    n, AKERR_MAX_ERR_VALUE - AKERR_LAST_ERRNO_VALUE);
+    /* We must have actually parsed both the codes and the ceiling. */
+    AKERR_CHECK(code_count > 0);
+    AKERR_CHECK(highest_code > 0);
+    AKERR_CHECK(max_err_value > 0);
+
+    /* Guard against parsing a different header than the one compiled in. */
+    AKERR_CHECK(max_err_value == (AKERR_MAX_ERR_VALUE - AKERR_LAST_ERRNO_VALUE));
+
+    /* The actual invariant: every defined code is indexable in the names table. */
+    AKERR_CHECK(max_err_value >= highest_code);
+
+    fprintf(stderr,
+	    "err_maxval ok (%d codes parsed, highest %s at +%d, max +%d)\n",
+	    code_count, highest_name, highest_code, max_err_value);
     return 0;
 }