detailed tests

tests/vector_altcap.c

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+/*
+ vector_altcap.c - Probes vector.h with a non-default DLIBC_VECTOR_INITIAL_CAPACITY.
+
+ The macro is read at include time, so exercising it needs a translation unit of
+ its own. Every function in vector.h is static inline, so this TU gets its own
+ copies built around the smaller constant while the vector_t layout stays
+ identical to the one in test_vector.c. That means a vector created here is a
+ perfectly ordinary vector to the rest of the program.
+
+ @attention This TU deliberately does not include dtest.h. The harness counters
+ are file-scope statics, so an assertion made here would be tallied separately
+ and never reach the summary. The probes below only gather observations, and
+ test_vector.c does the asserting.
+*/
+
+#define DLIBC_VECTOR_INITIAL_CAPACITY 1
+#include "../vector.h"
+
+/*
+ @brief Records the vector's capacity after each of count successive push_back() calls, starting from a freshly created vector.
+ @param out A buffer of at least count size_t values, filled with the capacity observed after each push.
+ @param count The number of pushes to perform.
+ @return 0 on success, -1 if out is NULL, count is 0, or any allocation fails.
+ @attention With DLIBC_VECTOR_INITIAL_CAPACITY at 1, the expected sequence is 1, 2, 4, 4, 8, 8, 8, 8, ...
+*/
+int vector_altcap_growth_sequence(size_t* out, size_t count) {
+    if (!out || count == 0) {
+        return -1;
+    }
+
+    vector_t* vec = vector_create(sizeof(int));
+    if (!vec) {
+        return -1;
+    }
+
+    for (size_t i = 0; i < count; ++i) {
+        int value = (int)i;
+        if (vector_push_back(vec, &value) != 0) {
+            vector_destroy(&vec);
+            return -1;
+        }
+
+        out[i] = vector_capacity(vec);
+    }
+
+    vector_destroy(&vec);
+    return 0;
+}
+
+/*
+ @brief Reports the capacity of a freshly created vector in this translation unit.
+ @return The initial capacity, or 0 if creation failed.
+*/
+size_t vector_altcap_initial_capacity(void) {
+    vector_t* vec = vector_create(sizeof(int));
+    if (!vec) {
+        return 0;
+    }
+
+    size_t capacity = vector_capacity(vec);
+    vector_destroy(&vec);
+    return capacity;
+}