Test init reservation failure

CMakeLists.txt

@@ -158,10 +158,18 @@ add_custom_command(
   VERBATIM
 )
 
+# More than one library target consumes the generated sources below. Route
+# them through one explicit prerequisite so parallel Make builds cannot invoke
+# the same generator twice and interleave writes to errno.c.
+add_custom_target(akerror_generated
+  DEPENDS ${GENERATED_ERRNO_C} ${GENERATED_AKERROR_H}
+)
+
 add_library(akerror SHARED
   src/error.c
   ${GENERATED_ERRNO_C}
 )
+add_dependencies(akerror akerror_generated)
 
 target_include_directories(akerror PUBLIC
   $<BUILD_INTERFACE:${GENERATED_DIR}/include>
@@ -200,6 +208,32 @@ set_target_properties(akerror PROPERTIES
 akerr_instrument_for_coverage(akerror)
 akerr_instrument_for_sanitizers(akerror)
 
+# akerr_init() must terminate if it cannot reserve the library-owned status
+# band. The production table sizes are deliberately PRIVATE, so exercise that
+# otherwise unreachable startup failure with a second library target whose
+# private registries cannot accept even the first reservation. Keeping this a
+# distinct target is the test: no compile definition leaks into consumers or
+# weakens the production library.
+add_library(akerror_init_failure SHARED
+  src/error.c
+  ${GENERATED_ERRNO_C}
+)
+add_dependencies(akerror_init_failure akerror_generated)
+target_include_directories(akerror_init_failure PUBLIC
+  ${GENERATED_DIR}/include
+)
+target_compile_definitions(akerror_init_failure
+  PUBLIC AKERR_USE_STDLIB=${AKERR_USE_STDLIB}
+  PRIVATE AKERR_STATUS_NAME_SLOTS=8
+  PRIVATE AKERR_MAX_RESERVED_STATUS_RANGES=0
+  PRIVATE ${AKERR_THREADS_DEFINE}
+)
+if(AKERR_THREAD_SAFE)
+    target_link_libraries(akerror_init_failure PRIVATE Threads::Threads)
+endif()
+akerr_instrument_for_coverage(akerror_init_failure)
+akerr_instrument_for_sanitizers(akerror_init_failure)
+
 # Each test is one source file in tests/ built into test_<name> and registered
 # as CTest <name>. Tests expected to abort (unhandled error / contract
 # violation) go in AKERR_WILL_FAIL_TESTS; all others must exit 0.
@@ -227,6 +261,7 @@ set(AKERR_TESTS
     err_registry_init_order
     err_status_exception
     err_copy_string
+    err_init_reservation_fatal
     err_library_status_fatal
     err_refcount_double_fail
     err_stacktrace_bounds
@@ -254,13 +289,18 @@ endif()
 set(AKERR_WILL_FAIL_TESTS
     err_trace
     err_improper_closure
+    err_init_reservation_fatal
     err_library_status_fatal
 )
 
 foreach(_test IN LISTS AKERR_TESTS)
     add_executable(test_${_test} tests/${_test}.c)
     target_include_directories(test_${_test} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/tests)
+    if(_test STREQUAL "err_init_reservation_fatal")
+        target_link_libraries(test_${_test} PRIVATE akerror_init_failure)
+    else()
         target_link_libraries(test_${_test} PRIVATE akerror)
+    endif()
     if(AKERR_THREAD_SAFE)
         target_link_libraries(test_${_test} PRIVATE Threads::Threads)
     endif()

src/error.c

@@ -88,7 +88,10 @@ typedef struct
 
 static akerr_StatusName akerr_status_names[AKERR_STATUS_NAME_SLOTS];
 static int akerr_status_name_count;
-static akerr_StatusRange akerr_status_ranges[AKERR_MAX_RESERVED_STATUS_RANGES];
+/* C has no portable zero-length arrays. Keep one unused physical slot when a
+ * test build sets the logical capacity to zero to drive init's fatal path. */
+static akerr_StatusRange akerr_status_ranges[
+    AKERR_MAX_RESERVED_STATUS_RANGES > 0 ? AKERR_MAX_RESERVED_STATUS_RANGES : 1];
 static int akerr_status_range_count;
 
 akerr_ErrorContext AKERR_ARRAY_ERROR[AKERR_MAX_ARRAY_ERROR];

tests/err_init_reservation_fatal.c

@@ -0,0 +1,20 @@
+#include "akerror.h"
+
+#include <stdio.h>
+
+/*
+ * This executable links to akerror_init_failure, a test-only library target
+ * with no status-range slots. The first reservation in akerr_init() must be
+ * terminal: continuing would leave every library status unowned and make all
+ * subsequent name registrations invalid.
+ *
+ * CTest marks this WILL_FAIL. Reaching the message and returning zero means
+ * initialization swallowed its own reservation failure.
+ */
+int main(void)
+{
+    akerr_init();
+
+    fprintf(stderr, "err_init_reservation_fatal: akerr_init did not terminate\n");
+    return 0;
+}