Feature: Use arena-allocation for memory handling

Arena allocation make deallocation of nested structed MUCH faster, and
improves the spatial locality of allocations. It makes no sense to
deallocate only parts of a JSON structure so arenas are a good fit here.

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "arena-allocator"]
+	path = arena-allocator
+	url = https://github.com/olemorud/arena-allocator.git

Makefile

@@ -10,15 +10,18 @@ COMPILER ?= gcc
 CC := gcc
 
 # -fsanitize={address,undefined}
-CFLAGS.gcc.debug := -Og -ggdb -fanalyzer -DBACKTRACE -rdynamic -fsanitize=address -fno-omit-frame-pointer
+CFLAGS.gcc.debug := -Og -ggdb -DBACKTRACE -rdynamic -fanalyzer -fsanitize=address -fno-omit-frame-pointer
 CFLAGS.gcc.release := -O3 -g -march=native -DNDEBUG
-CFLAGS.gcc := ${CFLAGS.gcc.${BUILD}} -Iinclude -Wall -Wextra -Wpedantic -Werror -Wno-strict-aliasing -fstack-protector-all -std=gnu11
+CFLAGS.gcc := ${CFLAGS.gcc.${BUILD}} -fstack-protector-all -std=gnu11 #-Wpedantic
 
 CFLAGS.clang.debug=-O0 -g3 -DBACKTRACE -rdynamic
 CFLAGS.clang.release=-O3 -g -march=native -DNDEBUG
-CFLAGS.clang=-Iinclude -Wall -Wextra -Wpedantic -Werror -Wno-strict-aliasing -fstack-protector-all ${CFLAGS.clang.${BUILD}}
+CFLAGS.clang=-Iinclude -Wno-strict-aliasing -fstack-protector-all ${CFLAGS.clang.${BUILD}}
 
-CFLAGS := ${CFLAGS.${COMPILER}}
+CFLAGS := ${CFLAGS.${COMPILER}} \
+		  -Iinclude -Iarena-allocator/include \
+		  -std=c2x \
+		  -Wall -Wextra -Wpedantic -Werror
 
 LD_PRELOAD:=
 
@@ -27,18 +30,24 @@ LD_PRELOAD:=
 BUILD_DIR := bin/${BUILD}
 
 OBJ_DIR := .obj/${BUILD}
-_OBJS := main.o parse.o json_value.o util.o
+_OBJS := main.o parse.o json_value.o util.o libarena.a
 OBJS := $(patsubst %,$(OBJ_DIR)/%,$(_OBJS))
 
-
 all : $(BUILD_DIR)/parse
 
-$(BUILD_DIR)/parse : $(OBJS) | $(BUILD_DIR) Makefile
+$(BUILD_DIR)/parse : $(OBJS) $(OBJ_DIR)/libarena.a | $(BUILD_DIR) Makefile
 	$(CC) $(CFLAGS) $^ $(LDFLAGS) $(LDLIBS) -o $@
 
-$(OBJ_DIR)/main.o : src/main.c | $(OBJ_DIR) Makefile
+$(OBJ_DIR)/main.o : src/main.c arena-allocator | $(OBJ_DIR) Makefile
 	$(CC) $(CFLAGS) $(LDFLAGS) $(LDLIBS) -c $< -o $@
 
+$(OBJ_DIR)/libarena.a : arena-allocator .gitmodules $(wildcard .git/modules/arena-allocator/HEAD) | $(OBJ_DIR) Makefile
+	(cd arena-allocator && make static)
+	cp --force arena-allocator/lib/libarena.a $(OBJ_DIR)/libarena.a
+
+arena-allocator : .gitmodules
+	git submodule update $@
+
 $(OBJ_DIR)/%.o : src/%.c include/%.h | $(OBJ_DIR) Makefile
 	$(CC) $(CFLAGS) $(LDFLAGS) $(LDLIBS) -c $< -o $@
 

compile_flags.txt

@@ -1,4 +1,5 @@
 -Iinclude
+-Iarena-allocator/include
 -Wall
 -Werror
 -Wpedantic

include/json_value.h

@@ -2,6 +2,7 @@
 #ifndef _JSON_VALUE_H
 #define _JSON_VALUE_H
 
+#include "arena.h"
 #include "config.h"
 #include <stdbool.h> // bool
 
@@ -9,7 +10,7 @@ typedef struct obj_entry {
     char const* key;
     struct json_value* val;
     struct obj_entry* next;
-} * __p_obj_entry;
+}* __p_obj_entry;
 
 typedef __p_obj_entry obj_t[OBJ_SIZE];
 
@@ -32,11 +33,11 @@ struct json_value {
 };
 
 void* obj_at(obj_t m, char* const key);
-bool obj_insert(obj_t m, char* const key, struct json_value* value);
+bool obj_insert(obj_t m, char* const key, struct json_value* value, arena_t* arena);
-void obj_delete(obj_t* m);
+void obj_delete(obj_t* m, arena_t* arena);
 
 void print_json(struct json_value val, int indent);
 
-void json_value_delete(struct json_value val);
+void json_value_delete(struct json_value val, arena_t* arena);
 
 #endif

include/parse.h

@@ -4,8 +4,9 @@
 
 #include "json_value.h"
 
+#include "arena.h"
 #include <stdio.h> // FILE*
 
-struct json_value parse_json_value(FILE* fp);
+struct json_value parse_json_value(FILE* fp, arena_t* arena);
 
 #endif

include/util.h

@@ -10,6 +10,6 @@ __attribute__((__noreturn__)) void err_ctx(int exit_code, FILE* fp, const char*
 void* malloc_or_die(size_t size);
 void* realloc_or_die(void* ptr, size_t size);
 void* calloc_or_die(size_t nmemb, size_t size);
-void print_trace();
+void print_trace(void);
 
 #endif

src/json_value.c

@@ -23,13 +23,11 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "arena.h"
 #include "json_value.h"
 #include "util.h"
 
-bool obj_insert(obj_t m, char* const key, struct json_value* value);
 size_t obj_hash(char const* str);
-void obj_delete(obj_t* m);
-void* obj_at(obj_t m, char* const key);
 
 void print_array(struct json_value** arr, int cur_indent, int indent_amount);
 void print_json_value(struct json_value val, int cur_indent, int indent_amount);
@@ -95,7 +93,7 @@ void* obj_at(obj_t m, char* const key)
    returns true if successful
    returns false if key already exists
 */
-bool obj_insert(obj_t m, char* const key, struct json_value* value)
+bool obj_insert(obj_t m, char* const key, struct json_value* value, arena_t* arena)
 {
     size_t i = obj_hash(key);
     struct obj_entry* cur = m[i];
@@ -119,7 +117,7 @@ bool obj_insert(obj_t m, char* const key, struct json_value* value)
         return false;
 
     /* populate new entry */
-    cur = malloc_or_die(sizeof(struct obj_entry));
+    cur = arena_alloc(arena, sizeof *cur);
     cur->key = key;
     cur->val = value;
     cur->next = m[i];
@@ -133,24 +131,24 @@ bool obj_insert(obj_t m, char* const key, struct json_value* value)
 /*
     Free memory allocated for json_value val
 */
-void json_value_delete(struct json_value val)
+void json_value_delete(struct json_value val, arena_t* arena)
 {
     switch (val.type) {
     case array:
         for (size_t i = 0; val.array[i] != NULL; i++) {
-            json_value_delete(*(val.array[i]));
+            json_value_delete(*(val.array[i]), arena);
-            free(val.array[i]);
+            arena_free(arena, val.array[i]);
         }
 
-        free(val.array);
+        arena_free(arena, val.array);
         break;
 
     case object:
-        obj_delete(val.object);
+        obj_delete(val.object, arena);
         break;
 
     case string:
-        free(val.string);
+        arena_free(arena, val.string);
         break;
 
     default:
@@ -159,26 +157,27 @@ void json_value_delete(struct json_value val)
 }
 
 /*
-    Free memory allocated for obj
+    Recursively deletes object and its children
 
-    Recursively deletes children objects
+    Included for completeness. To efficiently delete an object, reset
+    its associated arena instead.
 */
-void obj_delete(obj_t* m)
+void obj_delete(obj_t* m, arena_t* arena)
 {
     for (size_t i = 0; i < OBJ_SIZE; i++) {
         struct obj_entry *e = (*m)[i], *tmp;
 
         while (e != NULL) {
-            json_value_delete(*(e->val));
+            json_value_delete(*(e->val), arena);
-            free((char*)e->key);
+            arena_free(arena, (char*)e->key);
-            free(e->val);
+            arena_free(arena, e->val);
 
             tmp = e;
             e = e->next;
-            free(tmp);
+            arena_free(arena, tmp);
         }
     }
-    free(m);
+    arena_free(arena, m);
 }
 
 void add_indent(int n)

src/main.c

@@ -26,6 +26,8 @@
 
 int main(int argc, char* argv[])
 {
+    arena_t arena_default = arena_new();
+
     if (argc != 2) {
         errx(EXIT_FAILURE, "Usage: %s <file>", argv[0]);
     }
@@ -34,13 +36,13 @@ int main(int argc, char* argv[])
 
     FILE* fp = fopen(argv[1], "r");
 
-    struct json_value x = parse_json_value(fp);
+    struct json_value x = parse_json_value(fp, &arena_default);
 
     print_json(x, 1);
 
-    json_value_delete(x);
-
     fclose(fp);
 
+    arena_delete(&arena_default);
+
     return EXIT_SUCCESS;
 }

src/parse.c

@@ -20,24 +20,37 @@
 
 #include "parse.h"
 
+#include "arena.h"
 #include "config.h"
 #include "json_value.h"
 #include "util.h"
 
 #include <ctype.h> // isspace, isdigit
 #include <err.h> // err, errx
+#include <math.h> // NAN
 #include <stdio.h>
 #include <stdlib.h> // exit, EXIT_SUCCESS, EXIT_FAILURE
 #include <string.h> // strcmp
 
-char* read_string(FILE* fp);
-obj_t* read_object(FILE* fp);
-void discard_whitespace(FILE* fp);
 bool read_boolean(FILE* fp);
-void read_null(FILE* fp);
+char* read_string(FILE* fp, arena_t* arena);
 double read_number(FILE* fp);
-struct json_value** read_array(FILE* fp);
+obj_t* read_object(FILE* fp, arena_t* arena);
+struct json_value** read_array(FILE* fp, arena_t* arena);
 void discard_whitespace(FILE* fp);
+void read_null(FILE* fp);
+
+/*
+ghetto way to hunt down bugs
+#ifdef __GNUC__
+   #define _fgetc(fp) \
+       ({int retval; retval = fgetc(fp); fputc(retval, stderr); retval;})
+#else
+   #define _fgetc(fp) \
+       fgetc(fp)
+#endif
+*/
+#define _fgetc(fp) fgetc(fp)
 
 /*
     Consumes the next whitespace character in a file stream
@@ -47,7 +60,7 @@ void discard_whitespace(FILE* fp)
 {
     int c;
 
-    while (isspace(c = fgetc(fp))) {
+    while (isspace(c = _fgetc(fp))) {
         if (c == EOF)
             err_ctx(EARLY_EOF, fp, "(%s) unexpected EOF", __func__);
     }
@@ -64,10 +77,10 @@ void discard_whitespace(FILE* fp)
 
     These structures can be nested.
 */
-struct json_value parse_json_value(FILE* fp)
+struct json_value parse_json_value(FILE* fp, arena_t* arena)
 {
     discard_whitespace(fp);
-    int c = fgetc(fp);
+    int c = _fgetc(fp);
 
     struct json_value result = { 0 };
 
@@ -77,17 +90,17 @@ struct json_value parse_json_value(FILE* fp)
 
     case '{':
         result.type = object;
-        result.object = read_object(fp);
+        result.object = read_object(fp, arena);
         break;
 
     case '"':
         result.type = string;
-        result.string = read_string(fp);
+        result.string = read_string(fp, arena);
         break;
 
     case '[':
         result.type = array;
-        result.array = read_array(fp);
+        result.array = read_array(fp, arena);
         break;
 
     case 't':
@@ -127,21 +140,26 @@ struct json_value parse_json_value(FILE* fp)
 
     Consumes a JSON string from a file stream and returns a corresponding char*
 */
-char* read_string(FILE* fp)
+char* read_string(FILE* fp, arena_t* arena)
 {
     int c;
     size_t i = 0, result_size = 16;
-    char* result = malloc_or_die(result_size);
+    // char* result = malloc_or_die(result_size);
+    char* result = arena_alloc(arena, result_size);
 
     bool escaped = false;
 
     while (true) {
         if (i + 1 >= result_size) {
             result_size *= 2;
-            result = realloc_or_die(result, result_size);
+            result = arena_realloc_tail(arena, result_size);
+            if (result == NULL)
+                err_ctx(EXIT_FAILURE, fp, "could not allocate memory for string"
+                                          "%s",
+                    __func__);
         }
 
-        c = fgetc(fp);
+        c = _fgetc(fp);
 
         if (escaped) {
             escaped = false;
@@ -155,10 +173,9 @@ char* read_string(FILE* fp)
 
             case '"':
                 result[i++] = '\0';
-                return realloc_or_die(result, i);
+                return arena_realloc_tail(arena, i);
 
             case EOF:
-                free(result);
                 err_ctx(EARLY_EOF, fp, "(%s) unexpected EOF", __func__);
 
             default:
@@ -177,26 +194,25 @@ char* read_string(FILE* fp)
 
    Consumes a JSON object from a file stream and returns a corresponding obj_t
 */
-obj_t* read_object(FILE* fp)
+obj_t* read_object(FILE* fp, arena_t* arena)
 {
-    obj_t* result = calloc_or_die(1, sizeof(obj_t));
+    // obj_t* result = calloc_or_die(1, sizeof(obj_t));
+    obj_t* result = arena_calloc(arena, 1, sizeof *result);
     char* key;
 
     while (true) {
         /* read key */
         discard_whitespace(fp);
 
-        switch (fgetc(fp)) {
+        switch (_fgetc(fp)) {
         case EOF:
-            free(result);
             err_ctx(EARLY_EOF, fp, "(%s) unexpected EOF", __func__);
 
         default:
-            free(result);
             err_ctx(UNEXPECTED_CHAR, fp, "(%s) expected \"", __func__);
 
         case '"':
-            key = read_string(fp);
+            key = read_string(fp, arena);
             break;
 
         case '}':
@@ -206,39 +222,35 @@ obj_t* read_object(FILE* fp)
         /* check for ':' separator */
         discard_whitespace(fp);
 
-        switch (fgetc(fp)) {
+        switch (_fgetc(fp)) {
         case ':':
             break;
 
         case EOF:
-            free(result);
             err_ctx(EARLY_EOF, fp, "(%s) unexpected EOF", __func__);
 
         default:
-            free(result);
             err_ctx(UNEXPECTED_CHAR, fp, "(%s) expected ':'", __func__);
         }
 
         /* read value */
         discard_whitespace(fp);
 
-        struct json_value* val = calloc_or_die(1, sizeof(struct json_value));
+        // struct json_value* val = calloc_or_die(1, sizeof(struct json_value));
-        *val = parse_json_value(fp);
+        struct json_value* val = arena_calloc(arena, 1, sizeof *val);
+        *val = parse_json_value(fp, arena);
 
         /* insert key-value pair to obj */
-        if (!obj_insert(*result, key, val)) {
+        if (!obj_insert(*result, key, val, arena)) {
-            free(result);
+            fprintf(stderr, "failed to insert pair (%s, %p)\n", key, (void*)val);
-            free(val);
+            exit(EXIT_FAILURE);
-            errx(EXIT_FAILURE, "failed to insert pair (%s, %p)", key, (void*)val);
         }
 
         /* read separator or end of object */
         discard_whitespace(fp);
 
-        switch (fgetc(fp)) {
+        switch (_fgetc(fp)) {
         case EOF:
-            free(val);
-            free(result);
             err_ctx(EARLY_EOF, fp, "(%s) unexpected EOF", __func__);
 
         case ',':
@@ -248,8 +260,6 @@ obj_t* read_object(FILE* fp)
             return result;
 
         default:
-            free(val);
-            free(result);
             err_ctx(UNEXPECTED_CHAR, fp, "(%s) expected ',' or '}'", __func__);
         }
     }
@@ -264,42 +274,43 @@ obj_t* read_object(FILE* fp)
    Consumes a JSON array from a file stream and returns
    a NULL separated array of json_value pointers
 */
-struct json_value** read_array(FILE* fp)
+struct json_value** read_array(FILE* fp, arena_t* arena)
 {
     int c;
     size_t i = 0, output_size = 16;
-    struct json_value** output = malloc_or_die(output_size * sizeof(struct json_value*));
+    struct json_value** output = malloc_or_die(output_size * sizeof *output);
+    // struct json_value** output = arena_alloc(arena, output_size * sizeof *output);
 
     while (true) {
-        if (i + 1 >= output_size) {
+        if (i >= output_size) {
             output_size *= 2;
-            output = realloc_or_die(output, output_size * sizeof(struct json_value*));
+            // output = arena_realloc_tail(arena, output_size * sizeof *output);
+            output = realloc_or_die(output, output_size * sizeof *output);
         }
 
         discard_whitespace(fp);
-        c = fgetc(fp);
+        c = _fgetc(fp);
 
         switch (c) {
         case EOF:
-            free(output);
-
-            for (size_t j = 0; j < i; j++)
-                free(output[j]);
-
             err_ctx(EARLY_EOF, fp, "(%s) unexpected EOF", __func__);
             break;
 
         case ']':
             output[i++] = NULL;
-            return realloc_or_die(output, i * sizeof(struct json_value*));
+            struct json_value** x = arena_alloc(arena, i * sizeof *output);
+            memcpy(x, output, i * sizeof *output);
+            free(output);
+            return x;
 
         case ',':
             continue;
 
         default:
             ungetc(c, fp);
-            output[i] = malloc_or_die(sizeof(struct json_value));
+            // output[i] = malloc_or_die(sizeof(struct json_value));
-            *output[i] = parse_json_value(fp);
+            output[i] = arena_alloc(arena, sizeof *(output[i]));
+            *output[i] = parse_json_value(fp, arena);
             i++;
             break;
         }
@@ -365,15 +376,12 @@ bool read_boolean(FILE* fp)
 */
 double read_number(FILE* fp)
 {
-    static const unsigned long neg_nan = 0xFFFFFFFFFFFFFFFFULL;
+    double n = NAN;
-    double n = *(double*)&neg_nan;
 
     int n_read = fscanf(fp, "%lf", &n);
 
-    /* try to read as long instead */
+    if (n_read == 0)
-    if (n_read == 0) {
         err_ctx(UNEXPECTED_CHAR, fp, "(%s) number expected, found %lf", __func__, n);
-    }
 
     if (n_read == EOF)
         err_ctx(EARLY_EOF, fp, "(%s) unexpected EOF", __func__);

src/util.c

@@ -42,13 +42,12 @@ void* realloc_or_die(void* ptr, size_t size)
 {
     void* tmp = realloc(ptr, size);
 
-    if (ptr == NULL) {
+    if (tmp == NULL) {
         if (errno != 0) {
-            free(ptr);
             err(errno, "realloc_or_die failed");
         }
 
-        fprintf(stderr, "\nrealloc_or_die returned NULL but errno is 0, ptr: %p size: %zu\n", ptr, size);
+        fprintf(stderr, "\nrealloc_or_die returned NULL but errno is 0, ptr: %p size: %zu\n", tmp, size);
         exit(EXIT_FAILURE);
     }
 
@@ -67,9 +66,11 @@ void* calloc_or_die(size_t nmemb, size_t size)
 
 // from the glibc man pages
 // https://www.gnu.org/software/libc/manual/html_node/Backtraces.html
-void print_trace()
+void print_trace(void)
 {
-#ifdef BACKTRACE
+#ifndef BACKTRACE
+    return;
+#else
     void* array[500];
     char** strings;
     int size, i;
@@ -79,8 +80,9 @@ void print_trace()
 
     if (strings != NULL) {
         printf("\n\n=== Obtained %d stack frames. === \n", size);
-        for (i = 0; i < size; i++)
+        for (i = 0; i < size; i++) {
             printf("%s\n", strings[i]);
+        }
     }
 
     free(strings);