Introduce the emitter module.

The emitter can be used to produce structured json or tabular output.  For now
it has no uses; in subsequent commits, I'll begin transitioning stats printing
code over.

3 files changed, 733 insertions, 0 deletions

diff --git a/Makefile.in b/Makefile.in
index aefd6d87..e229196c 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -168,6 +168,7 @@ TESTS_UNIT := \
 	$(srcroot)test/unit/ckh.c \
 	$(srcroot)test/unit/decay.c \
 	$(srcroot)test/unit/div.c \
+	$(srcroot)test/unit/emitter.c \
 	$(srcroot)test/unit/extent_quantize.c \
 	$(srcroot)test/unit/fork.c \
 	$(srcroot)test/unit/hash.c \
diff --git a/include/jemalloc/internal/emitter.h b/include/jemalloc/internal/emitter.h
new file mode 100644
index 00000000..c82dbdb1
--- /dev/null
+++ b/include/jemalloc/internal/emitter.h
@@ -0,0 +1,381 @@
+#ifndef JEMALLOC_INTERNAL_EMITTER_H
+#define JEMALLOC_INTERNAL_EMITTER_H
+
+typedef enum emitter_output_e emitter_output_t;
+enum emitter_output_e {
+	emitter_output_json,
+	emitter_output_table
+};
+
+typedef enum emitter_justify_e emitter_justify_t;
+enum emitter_justify_e {
+	emitter_justify_left,
+	emitter_justify_right,
+	/* Not for users; just to pass to internal functions. */
+	emitter_justify_none
+};
+
+typedef enum emitter_type_e emitter_type_t;
+enum emitter_type_e {
+	emitter_type_bool,
+	emitter_type_int,
+	emitter_type_unsigned,
+	emitter_type_uint32,
+	emitter_type_uint64,
+	emitter_type_size,
+	emitter_type_ssize,
+	emitter_type_string,
+};
+
+typedef struct emitter_s emitter_t;
+struct emitter_s {
+	emitter_output_t output;
+	/* The output information. */
+	void (*write_cb)(void *, const char *);
+	void *cbopaque;
+	int nesting_depth;
+	/* True if we've already emitted a value at the given depth. */
+	bool item_at_depth;
+};
+
+static inline void
+emitter_init(emitter_t *emitter, emitter_output_t emitter_output,
+    void (*write_cb)(void *, const char *), void *cbopaque) {
+	emitter->output = emitter_output;
+	emitter->write_cb = write_cb;
+	emitter->cbopaque = cbopaque;
+	emitter->item_at_depth = false;
+	emitter->nesting_depth = 0;
+}
+
+/* Internal convenience function.  Write to the emitter the given string. */
+JEMALLOC_FORMAT_PRINTF(2, 3)
+static inline void
+emitter_printf(emitter_t *emitter, const char *format, ...) {
+	va_list ap;
+
+	va_start(ap, format);
+	malloc_vcprintf(emitter->write_cb, emitter->cbopaque, format, ap);
+	va_end(ap);
+}
+
+/* Write to the emitter the given string, but only in table mode. */
+JEMALLOC_FORMAT_PRINTF(2, 3)
+static inline void
+emitter_table_printf(emitter_t *emitter, const char *format, ...) {
+	if (emitter->output == emitter_output_table) {
+		va_list ap;
+		va_start(ap, format);
+		malloc_vcprintf(emitter->write_cb, emitter->cbopaque, format, ap);
+		va_end(ap);
+	}
+}
+
+static inline void
+emitter_gen_fmt(char *out_fmt, size_t out_size, const char *fmt_specifier,
+    emitter_justify_t justify, int width) {
+	size_t written;
+	if (justify == emitter_justify_none) {
+		written = malloc_snprintf(out_fmt, out_size,
+		    "%%%s", fmt_specifier);
+	} else if (justify == emitter_justify_left) {
+		written = malloc_snprintf(out_fmt, out_size,
+		    "%%-%d%s", width, fmt_specifier);
+	} else {
+		written = malloc_snprintf(out_fmt, out_size,
+		    "%%%d%s", width, fmt_specifier);
+	}
+	/* Only happens in case of bad format string, which *we* choose. */
+	assert(written <  out_size);
+}
+
+/*
+ * Internal.  Emit the given value type in the relevant encoding (so that the
+ * bool true gets mapped to json "true", but the string "true" gets mapped to
+ * json "\"true\"", for instance.
+ *
+ * Width is ignored if justify is emitter_justify_none.
+ */
+static inline void
+emitter_print_value(emitter_t *emitter, emitter_justify_t justify, int width,
+    emitter_type_t value_type, const void *value) {
+	size_t str_written;
+#define BUF_SIZE 256
+#define FMT_SIZE 10
+	/*
+	 * We dynamically generate a format string to emit, to let us use the
+	 * snprintf machinery.  This is kinda hacky, but gets the job done
+	 * quickly without having to think about the various snprintf edge
+	 * cases.
+	 */
+	char fmt[FMT_SIZE];
+	char buf[BUF_SIZE];
+
+#define EMIT_SIMPLE(type, format)					\
+	emitter_gen_fmt(fmt, FMT_SIZE, format, justify, width);		\
+	emitter_printf(emitter, fmt, *(const type *)value);		\
+
+	switch (value_type) {
+	case emitter_type_bool:
+		emitter_gen_fmt(fmt, FMT_SIZE, "s", justify, width);
+		emitter_printf(emitter, fmt, *(const bool *)value ?
+		    "true" : "false");
+		break;
+	case emitter_type_int:
+		EMIT_SIMPLE(int, "d")
+		break;
+	case emitter_type_unsigned:
+		EMIT_SIMPLE(unsigned, "u")
+		break;
+	case emitter_type_ssize:
+		EMIT_SIMPLE(ssize_t, "zd")
+		break;
+	case emitter_type_size:
+		EMIT_SIMPLE(size_t, "zu")
+		break;
+	case emitter_type_string:
+		str_written = malloc_snprintf(buf, BUF_SIZE, "\"%s\"",
+		    *(const char *const *)value);
+		/*
+		 * We control the strings we output; we shouldn't get anything
+		 * anywhere near the fmt size.
+		 */
+		assert(str_written < BUF_SIZE);
+
+		/*
+		 * We don't support justified quoted string primitive values for
+		 * now. Fortunately, we don't want to emit them.
+		 */
+
+		emitter_gen_fmt(fmt, FMT_SIZE, "s", justify, width);
+		emitter_printf(emitter, fmt, buf);
+		break;
+	case emitter_type_uint32:
+		EMIT_SIMPLE(uint32_t, FMTu32)
+		break;
+	case emitter_type_uint64:
+		EMIT_SIMPLE(uint64_t, FMTu64)
+		break;
+	default:
+		unreachable();
+	}
+#undef BUF_SIZE
+#undef FMT_SIZE
+}
+
+
+/* Internal functions.  In json mode, tracks nesting state. */
+static inline void
+emitter_nest_inc(emitter_t *emitter) {
+	emitter->nesting_depth++;
+	emitter->item_at_depth = false;
+}
+
+static inline void
+emitter_nest_dec(emitter_t *emitter) {
+	emitter->nesting_depth--;
+	emitter->item_at_depth = true;
+}
+
+static inline void
+emitter_indent(emitter_t *emitter) {
+	int amount = emitter->nesting_depth;
+	const char *indent_str;
+	if (emitter->output == emitter_output_json) {
+		indent_str = "\t";
+	} else {
+		amount *= 2;
+		indent_str = " ";
+	}
+	for (int i = 0; i < amount; i++) {
+		emitter_printf(emitter, "%s", indent_str);
+	}
+}
+
+static inline void
+emitter_json_key_prefix(emitter_t *emitter) {
+	emitter_printf(emitter, "%s\n", emitter->item_at_depth ? "," : "");
+	emitter_indent(emitter);
+}
+
+static inline void
+emitter_begin(emitter_t *emitter) {
+	if (emitter->output == emitter_output_json) {
+		assert(emitter->nesting_depth == 0);
+		emitter_printf(emitter, "{");
+		emitter_nest_inc(emitter);
+	} else {
+		// tabular init
+		emitter_printf(emitter, "");
+	}
+}
+
+static inline void
+emitter_end(emitter_t *emitter) {
+	if (emitter->output == emitter_output_json) {
+		assert(emitter->nesting_depth == 1);
+		emitter_nest_dec(emitter);
+		emitter_printf(emitter, "\n}\n");
+	}
+}
+
+/*
+ * Note emits a different kv pair as well, but only in table mode.  Omits the
+ * note if table_note_key is NULL.
+ */
+static inline void
+emitter_kv_note(emitter_t *emitter, const char *json_key, const char *table_key,
+    emitter_type_t value_type, const void *value,
+    const char *table_note_key, emitter_type_t table_note_value_type,
+    const void *table_note_value) {
+	if (emitter->output == emitter_output_json) {
+		assert(emitter->nesting_depth > 0);
+		emitter_json_key_prefix(emitter);
+		emitter_printf(emitter, "\"%s\": ", json_key);
+		emitter_print_value(emitter, emitter_justify_none, -1,
+		    value_type, value);
+	} else {
+		emitter_indent(emitter);
+		emitter_printf(emitter, "%s: ", table_key);
+		emitter_print_value(emitter, emitter_justify_none, -1,
+		    value_type, value);
+		if (table_note_key != NULL) {
+			emitter_printf(emitter, " (%s: ", table_note_key);
+			emitter_print_value(emitter, emitter_justify_none, -1,
+			    table_note_value_type, table_note_value);
+			emitter_printf(emitter, ")");
+		}
+		emitter_printf(emitter, "\n");
+	}
+	emitter->item_at_depth = true;
+}
+
+static inline void
+emitter_kv(emitter_t *emitter, const char *json_key, const char *table_key,
+    emitter_type_t value_type, const void *value) {
+	emitter_kv_note(emitter, json_key, table_key, value_type, value, NULL,
+	    emitter_type_bool, NULL);
+}
+
+static inline void
+emitter_json_kv(emitter_t *emitter, const char *json_key,
+    emitter_type_t value_type, const void *value) {
+	if (emitter->output == emitter_output_json) {
+		emitter_kv(emitter, json_key, NULL, value_type, value);
+	}
+}
+
+static inline void
+emitter_table_kv(emitter_t *emitter, const char *table_key,
+    emitter_type_t value_type, const void *value) {
+	if (emitter->output == emitter_output_table) {
+		emitter_kv(emitter, NULL, table_key, value_type, value);
+	}
+}
+
+static inline void
+emitter_dict_begin(emitter_t *emitter, const char *json_key,
+    const char *table_header) {
+	if (emitter->output == emitter_output_json) {
+		emitter_json_key_prefix(emitter);
+		emitter_printf(emitter, "\"%s\": {", json_key);
+		emitter_nest_inc(emitter);
+	} else {
+		emitter_indent(emitter);
+		emitter_printf(emitter, "%s\n", table_header);
+		emitter_nest_inc(emitter);
+	}
+}
+
+static inline void
+emitter_dict_end(emitter_t *emitter) {
+	if (emitter->output == emitter_output_json) {
+		assert(emitter->nesting_depth > 0);
+		emitter_nest_dec(emitter);
+		emitter_printf(emitter, "\n");
+		emitter_indent(emitter);
+		emitter_printf(emitter, "}");
+	} else {
+		emitter_nest_dec(emitter);
+	}
+}
+
+static inline void
+emitter_json_dict_begin(emitter_t *emitter, const char *json_key) {
+	if (emitter->output == emitter_output_json) {
+		emitter_dict_begin(emitter, json_key, NULL);
+	}
+}
+
+static inline void
+emitter_json_dict_end(emitter_t *emitter) {
+	if (emitter->output == emitter_output_json) {
+		emitter_dict_end(emitter);
+	}
+}
+
+static inline void
+emitter_table_dict_begin(emitter_t *emitter, const char *table_key) {
+	if (emitter->output == emitter_output_table) {
+		emitter_dict_begin(emitter, NULL, table_key);
+	}
+}
+
+static inline void
+emitter_table_dict_end(emitter_t *emitter) {
+	if (emitter->output == emitter_output_table) {
+		emitter_dict_end(emitter);
+	}
+}
+
+static inline void
+emitter_json_arr_begin(emitter_t *emitter, const char *json_key) {
+	if (emitter->output == emitter_output_json) {
+		emitter_json_key_prefix(emitter);
+		emitter_printf(emitter, "\"%s\": [", json_key);
+		emitter_nest_inc(emitter);
+	}
+}
+
+static inline void
+emitter_json_arr_end(emitter_t *emitter) {
+	if (emitter->output == emitter_output_json) {
+		assert(emitter->nesting_depth > 0);
+		emitter_nest_dec(emitter);
+		emitter_printf(emitter, "\n");
+		emitter_indent(emitter);
+		emitter_printf(emitter, "]");
+	}
+}
+
+static inline void
+emitter_json_arr_obj_begin(emitter_t *emitter) {
+	if (emitter->output == emitter_output_json) {
+		emitter_json_key_prefix(emitter);
+		emitter_printf(emitter, "{");
+		emitter_nest_inc(emitter);
+	}
+}
+
+static inline void
+emitter_json_arr_obj_end(emitter_t *emitter) {
+	if (emitter->output == emitter_output_json) {
+		assert(emitter->nesting_depth > 0);
+		emitter_nest_dec(emitter);
+		emitter_printf(emitter, "\n");
+		emitter_indent(emitter);
+		emitter_printf(emitter, "}");
+	}
+}
+
+static inline void
+emitter_json_arr_value(emitter_t *emitter, emitter_type_t value_type,
+    const void *value) {
+	if (emitter->output == emitter_output_json) {
+		emitter_json_key_prefix(emitter);
+		emitter_print_value(emitter, emitter_justify_none, -1,
+		    value_type, value);
+	}
+}
+
+#endif /* JEMALLOC_INTERNAL_EMITTER_H */
diff --git a/test/unit/emitter.c b/test/unit/emitter.c
new file mode 100644
index 00000000..c2216b22
--- /dev/null
+++ b/test/unit/emitter.c
@@ -0,0 +1,351 @@
+#include "test/jemalloc_test.h"
+#include "jemalloc/internal/emitter.h"
+
+/*
+ * This is so useful for debugging and feature work, we'll leave printing
+ * functionality committed but disabled by default.
+ */
+/* Print the text as it will appear. */
+static bool print_raw = false;
+/* Print the text escaped, so it can be copied back into the test case. */
+static bool print_escaped = false;
+
+typedef struct buf_descriptor_s buf_descriptor_t;
+struct buf_descriptor_s {
+	char *buf;
+	size_t len;
+	bool mid_quote;
+};
+
+/*
+ * Forwards all writes to the passed-in buf_v (which should be cast from a
+ * buf_descriptor_t *).
+ */
+static void
+forwarding_cb(void *buf_descriptor_v, const char *str) {
+	buf_descriptor_t *buf_descriptor = (buf_descriptor_t *)buf_descriptor_v;
+
+	if (print_raw) {
+		malloc_printf("%s", str);
+	}
+	if (print_escaped) {
+		const char *it = str;
+		while (*it != '\0') {
+			if (!buf_descriptor->mid_quote) {
+				malloc_printf("\"");
+				buf_descriptor->mid_quote = true;
+			}
+			switch (*it) {
+			case '\\':
+				malloc_printf("\\");
+				break;
+			case '\"':
+				malloc_printf("\\\"");
+				break;
+			case '\t':
+				malloc_printf("\\t");
+				break;
+			case '\n':
+				malloc_printf("\\n\"\n");
+				buf_descriptor->mid_quote = false;
+				break;
+			default:
+				malloc_printf("%c", *it);
+			}
+			it++;
+		}
+	}
+
+	size_t written = malloc_snprintf(buf_descriptor->buf,
+	    buf_descriptor->len, "%s", str);
+	assert_zu_eq(written, strlen(str), "Buffer overflow!");
+	buf_descriptor->buf += written;
+	buf_descriptor->len -= written;
+	assert_zu_gt(buf_descriptor->len, 0, "Buffer out of space!");
+}
+
+static void
+assert_emit_output(void (*emit_fn)(emitter_t *),
+    const char *expected_json_output, const char *expected_table_output) {
+	emitter_t emitter;
+	char buf[MALLOC_PRINTF_BUFSIZE];
+	buf_descriptor_t buf_descriptor;
+
+	buf_descriptor.buf = buf;
+	buf_descriptor.len = MALLOC_PRINTF_BUFSIZE;
+	buf_descriptor.mid_quote = false;
+
+	emitter_init(&emitter, emitter_output_json, &forwarding_cb,
+	    &buf_descriptor);
+	(*emit_fn)(&emitter);
+	assert_str_eq(expected_json_output, buf, "json output failure");
+
+	buf_descriptor.buf = buf;
+	buf_descriptor.len = MALLOC_PRINTF_BUFSIZE;
+	buf_descriptor.mid_quote = false;
+
+	emitter_init(&emitter, emitter_output_table, &forwarding_cb,
+	    &buf_descriptor);
+	(*emit_fn)(&emitter);
+	assert_str_eq(expected_table_output, buf, "table output failure");
+}
+
+static void
+emit_dict(emitter_t *emitter) {
+	bool b_false = false;
+	bool b_true = true;
+	int i_123 = 123;
+	const char *str = "a string";
+
+	emitter_begin(emitter);
+	emitter_dict_begin(emitter, "foo", "This is the foo table:");
+	emitter_kv(emitter, "abc", "ABC", emitter_type_bool, &b_false);
+	emitter_kv(emitter, "def", "DEF", emitter_type_bool, &b_true);
+	emitter_kv_note(emitter, "ghi", "GHI", emitter_type_int, &i_123,
+	    "note_key1", emitter_type_string, &str);
+	emitter_kv_note(emitter, "jkl", "JKL", emitter_type_string, &str,
+	    "note_key2", emitter_type_bool, &b_false);
+	emitter_dict_end(emitter);
+	emitter_end(emitter);
+}
+static const char *dict_json =
+"{\n"
+"\t\"foo\": {\n"
+"\t\t\"abc\": false,\n"
+"\t\t\"def\": true,\n"
+"\t\t\"ghi\": 123,\n"
+"\t\t\"jkl\": \"a string\"\n"
+"\t}\n"
+"}\n";
+static const char *dict_table =
+"This is the foo table:\n"
+"  ABC: false\n"
+"  DEF: true\n"
+"  GHI: 123 (note_key1: \"a string\")\n"
+"  JKL: \"a string\" (note_key2: false)\n";
+
+TEST_BEGIN(test_dict) {
+	assert_emit_output(&emit_dict, dict_json, dict_table);
+}
+TEST_END
+
+static void
+emit_table_printf(emitter_t *emitter) {
+	emitter_begin(emitter);
+	emitter_table_printf(emitter, "Table note 1\n");
+	emitter_table_printf(emitter, "Table note 2 %s\n",
+	    "with format string");
+	emitter_end(emitter);
+}
+
+static const char *table_printf_json =
+"{\n"
+"}\n";
+
+static const char *table_printf_table =
+"Table note 1\n"
+"Table note 2 with format string\n";
+
+TEST_BEGIN(test_table_printf) {
+	assert_emit_output(&emit_table_printf, table_printf_json,
+	    table_printf_table);
+}
+TEST_END
+
+static void emit_nested_dict(emitter_t *emitter) {
+	int val = 123;
+	emitter_begin(emitter);
+	emitter_dict_begin(emitter, "json1", "Dict 1");
+	emitter_dict_begin(emitter, "json2", "Dict 2");
+	emitter_kv(emitter, "primitive", "A primitive", emitter_type_int, &val);
+	emitter_dict_end(emitter); /* Close 2 */
+	emitter_dict_begin(emitter, "json3", "Dict 3");
+	emitter_dict_end(emitter); /* Close 3 */
+	emitter_dict_end(emitter); /* Close 1 */
+	emitter_dict_begin(emitter, "json4", "Dict 4");
+	emitter_kv(emitter, "primitive", "Another primitive",
+	    emitter_type_int, &val);
+	emitter_dict_end(emitter); /* Close 4 */
+	emitter_end(emitter);
+}
+
+static const char *nested_dict_json =
+"{\n"
+"\t\"json1\": {\n"
+"\t\t\"json2\": {\n"
+"\t\t\t\"primitive\": 123\n"
+"\t\t},\n"
+"\t\t\"json3\": {\n"
+"\t\t}\n"
+"\t},\n"
+"\t\"json4\": {\n"
+"\t\t\"primitive\": 123\n"
+"\t}\n"
+"}\n";
+
+static const char *nested_dict_table =
+"Dict 1\n"
+"  Dict 2\n"
+"    A primitive: 123\n"
+"  Dict 3\n"
+"Dict 4\n"
+"  Another primitive: 123\n";
+
+TEST_BEGIN(test_nested_dict) {
+	assert_emit_output(&emit_nested_dict, nested_dict_json,
+	    nested_dict_table);
+}
+TEST_END
+
+static void
+emit_types(emitter_t *emitter) {
+	bool b = false;
+	int i = -123;
+	unsigned u = 123;
+	ssize_t zd = -456;
+	size_t zu = 456;
+	const char *str = "string";
+	uint32_t u32 = 789;
+	uint64_t u64 = 10000000000ULL;
+
+	emitter_begin(emitter);
+	emitter_kv(emitter, "k1", "K1", emitter_type_bool, &b);
+	emitter_kv(emitter, "k2", "K2", emitter_type_int, &i);
+	emitter_kv(emitter, "k3", "K3", emitter_type_unsigned, &u);
+	emitter_kv(emitter, "k4", "K4", emitter_type_ssize, &zd);
+	emitter_kv(emitter, "k5", "K5", emitter_type_size, &zu);
+	emitter_kv(emitter, "k6", "K6", emitter_type_string, &str);
+	emitter_kv(emitter, "k7", "K7", emitter_type_uint32, &u32);
+	emitter_kv(emitter, "k8", "K8", emitter_type_uint64, &u64);
+	emitter_end(emitter);
+}
+
+static const char *types_json =
+"{\n"
+"\t\"k1\": false,\n"
+"\t\"k2\": -123,\n"
+"\t\"k3\": 123,\n"
+"\t\"k4\": -456,\n"
+"\t\"k5\": 456,\n"
+"\t\"k6\": \"string\",\n"
+"\t\"k7\": 789,\n"
+"\t\"k8\": 10000000000\n"
+"}\n";
+
+static const char *types_table =
+"K1: false\n"
+"K2: -123\n"
+"K3: 123\n"
+"K4: -456\n"
+"K5: 456\n"
+"K6: \"string\"\n"
+"K7: 789\n"
+"K8: 10000000000\n";
+
+TEST_BEGIN(test_types) {
+	assert_emit_output(&emit_types, types_json, types_table);
+}
+TEST_END
+
+static void
+emit_modal(emitter_t *emitter) {
+	int val = 123;
+	emitter_begin(emitter);
+	emitter_dict_begin(emitter, "j0", "T0");
+	emitter_json_dict_begin(emitter, "j1");
+	emitter_kv(emitter, "i1", "I1", emitter_type_int, &val);
+	emitter_json_kv(emitter, "i2", emitter_type_int, &val);
+	emitter_table_kv(emitter, "I3", emitter_type_int, &val);
+	emitter_table_dict_begin(emitter, "T1");
+	emitter_kv(emitter, "i4", "I4", emitter_type_int, &val);
+	emitter_json_dict_end(emitter); /* Close j1 */
+	emitter_kv(emitter, "i5", "I5", emitter_type_int, &val);
+	emitter_table_dict_end(emitter); /* Close T1 */
+	emitter_kv(emitter, "i6", "I6", emitter_type_int, &val);
+	emitter_dict_end(emitter); /* Close j0 / T0 */
+	emitter_end(emitter);
+}
+
+const char *modal_json =
+"{\n"
+"\t\"j0\": {\n"
+"\t\t\"j1\": {\n"
+"\t\t\t\"i1\": 123,\n"
+"\t\t\t\"i2\": 123,\n"
+"\t\t\t\"i4\": 123\n"
+"\t\t},\n"
+"\t\t\"i5\": 123,\n"
+"\t\t\"i6\": 123\n"
+"\t}\n"
+"}\n";
+
+const char *modal_table =
+"T0\n"
+"  I1: 123\n"
+"  I3: 123\n"
+"  T1\n"
+"    I4: 123\n"
+"    I5: 123\n"
+"  I6: 123\n";
+
+TEST_BEGIN(test_modal) {
+	assert_emit_output(&emit_modal, modal_json, modal_table);
+}
+TEST_END
+
+static void
+emit_json_arr(emitter_t *emitter) {
+	int ival = 123;
+
+	emitter_begin(emitter);
+	emitter_json_dict_begin(emitter, "dict");
+	emitter_json_arr_begin(emitter, "arr");
+	emitter_json_arr_obj_begin(emitter);
+	emitter_json_kv(emitter, "foo", emitter_type_int, &ival);
+	emitter_json_arr_obj_end(emitter); /* Close arr[0] */
+	/* arr[1] and arr[2] are primitives. */
+	emitter_json_arr_value(emitter, emitter_type_int, &ival);
+	emitter_json_arr_value(emitter, emitter_type_int, &ival);
+	emitter_json_arr_obj_begin(emitter);
+	emitter_json_kv(emitter, "bar", emitter_type_int, &ival);
+	emitter_json_kv(emitter, "baz", emitter_type_int, &ival);
+	emitter_json_arr_obj_end(emitter); /* Close arr[3]. */
+	emitter_json_arr_end(emitter); /* Close arr. */
+	emitter_json_dict_end(emitter); /* Close dict. */
+	emitter_end(emitter);
+}
+
+static const char *json_arr_json =
+"{\n"
+"\t\"dict\": {\n"
+"\t\t\"arr\": [\n"
+"\t\t\t{\n"
+"\t\t\t\t\"foo\": 123\n"
+"\t\t\t},\n"
+"\t\t\t123,\n"
+"\t\t\t123,\n"
+"\t\t\t{\n"
+"\t\t\t\t\"bar\": 123,\n"
+"\t\t\t\t\"baz\": 123\n"
+"\t\t\t}\n"
+"\t\t]\n"
+"\t}\n"
+"}\n";
+
+static const char *json_arr_table = "";
+
+TEST_BEGIN(test_json_arr) {
+	assert_emit_output(&emit_json_arr, json_arr_json, json_arr_table);
+}
+TEST_END
+
+int
+main(void) {
+	return test_no_reentrancy(
+	    test_dict,
+	    test_table_printf,
+	    test_nested_dict,
+	    test_types,
+	    test_modal,
+	    test_json_arr);
+}