c: Add Boehm garbage collector

By default, garbage collection is enabled.  You can run:

    make USE_GC=

to build the C implementation without garbage collection.

README.md

@@ -144,7 +144,8 @@ bash stepX_YYY.sh
 ### C
 
 The C implementation of mal requires the following libraries (lib and
-header packages): glib, libffi6 and either the libedit or GNU readline library.
+header packages): glib, libffi6, libgc, and either the libedit or GNU readline
+library.
 
 ```
 cd c

c/Dockerfile

@@ -25,4 +25,4 @@ WORKDIR /mal
 RUN apt-get -y install g++
 
 # Libraries needed for the C impl
-RUN apt-get -y install libglib2.0 libglib2.0-dev libffi-dev
+RUN apt-get -y install libglib2.0 libglib2.0-dev libffi-dev libgc-dev

c/Makefile

@@ -1,4 +1,5 @@
 USE_READLINE ?=
+USE_GC ?= 1
 CFLAGS += -g -O2
 LDFLAGS += -g
 
@@ -38,6 +39,12 @@ RL_LIBRARY ?= readline
 CFLAGS += -DUSE_READLINE=1
 endif
 
+ifeq (,$(USE_GC))
+else
+CFLAGS += -DUSE_GC=1
+LDFLAGS += -lgc
+endif
+
 CFLAGS += $(GLIB_CFLAGS)
 LDFLAGS += -l$(RL_LIBRARY) $(GLIB_LDFLAGS) -ldl -lffi 
 

c/core.c

@@ -96,8 +96,8 @@ MalVal *prn(MalVal *args) {
     assert_type(args, MAL_LIST|MAL_VECTOR,
                 "prn called with non-sequential args");
     char *repr = _pr_str_args(args, " ", 1);
-    g_print("%s\n", repr);
-    free(repr);
+    puts(repr);
+    MAL_GC_FREE(repr);
     return &mal_nil;
 }
 
@@ -107,8 +107,8 @@ MalVal *println(MalVal *args) {
     assert_type(args, MAL_LIST|MAL_VECTOR,
                 "println called with non-sequential args");
     char *repr = _pr_str_args(args, " ", 0);
-    g_print("%s\n", repr);
-    free(repr);
+    puts(repr);
+    MAL_GC_FREE(repr);
     return &mal_nil;
 }
 
@@ -135,7 +135,7 @@ char *slurp_raw(char *path) {
     if (fstat(fd, &fst) < 0) {
         abort("slurp failed to stat '%s'", path);
     }
-    data = malloc(fst.st_size+1);
+    data = MAL_GC_MALLOC(fst.st_size+1);
     sz = read(fd, data, fst.st_size);
     if (sz < fst.st_size) {
         abort("slurp failed to read '%s'", path);

c/env.c

@@ -4,7 +4,7 @@
 // Env
 
 Env *new_env(Env *outer, MalVal* binds, MalVal *exprs) {
-    Env *e = malloc(sizeof(Env));
+    Env *e = MAL_GC_MALLOC(sizeof(Env));
     e->table = g_hash_table_new(g_str_hash, g_str_equal);
     e->outer = outer;
 

c/printer.c

@@ -29,13 +29,13 @@ char *_pr_str_hash_map(MalVal *obj, int print_readably) {
         } else {
             repr_tmp2 = repr;
             repr = g_strdup_printf("%s %s %s", repr_tmp2, (char*)key2, repr_tmp1);
-            free(repr_tmp2);
+            MAL_GC_FREE(repr_tmp2);
         }
-        free(repr_tmp1);
+        MAL_GC_FREE(repr_tmp1);
     }
     repr_tmp2 = repr;
     repr = g_strdup_printf("%s}", repr_tmp2);
-    free(repr_tmp2);
+    MAL_GC_FREE(repr_tmp2);
     return repr;
 }
 
@@ -51,13 +51,13 @@ char *_pr_str_list(MalVal *obj, int print_readably, char start, char end) {
         } else {
             repr_tmp2 = repr;
             repr = g_strdup_printf("%s %s", repr_tmp2, repr_tmp1);
-            free(repr_tmp2);
+            MAL_GC_FREE(repr_tmp2);
         }
-        free(repr_tmp1);
+        MAL_GC_FREE(repr_tmp1);
     }
     repr_tmp2 = repr;
     repr = g_strdup_printf("%s%c", repr_tmp2, end);
-    free(repr_tmp2);
+    MAL_GC_FREE(repr_tmp2);
     return repr;
 }
 
@@ -84,7 +84,7 @@ char *_pr_str(MalVal *obj, int print_readably) {
         } else if (print_readably) {
             char *repr_tmp = g_strescape(obj->val.string, "");
             repr = g_strdup_printf("\"%s\"", repr_tmp);
-            free(repr_tmp);
+            MAL_GC_FREE(repr_tmp);
         } else {
             repr = g_strdup_printf("%s", obj->val.string);
         }
@@ -139,13 +139,16 @@ char *_pr_str_args(MalVal *args, char *sep, int print_readably) {
         if (i != 0) {
             repr2 = repr;
             repr = g_strdup_printf("%s%s", repr2, sep);
-            free(repr2);
+            MAL_GC_FREE(repr2);
         }
         repr2 = repr;
         repr = g_strdup_printf("%s%s",
                                repr2, _pr_str(obj, print_readably));
-        free(repr2);
+        MAL_GC_FREE(repr2);
     }
-    return repr;
+    char* res = MAL_GC_STRDUP(repr);
+    MAL_GC_FREE(repr);
+    // TODO - check why STRDUP was needed here
+    return res;
 }
 

c/reader.c

@@ -13,7 +13,7 @@
 MalVal *read_form(Reader *reader);
 
 Reader *reader_new() {
-    Reader *reader = (Reader*)malloc(sizeof(Reader));
+    Reader *reader = (Reader*)MAL_GC_MALLOC(sizeof(Reader));
     reader->array = g_array_sized_new(TRUE, FALSE, sizeof(char *), 8);
     reader->position = 0;
     return reader;
@@ -39,10 +39,10 @@ char *reader_next(Reader *reader) {
 void reader_free(Reader *reader) {
     int i;
     for(i=0; i < reader->array->len; i++) {
-        free(g_array_index(reader->array, char*, i));
+        MAL_GC_FREE(g_array_index(reader->array, char*, i));
     }
-    g_array_free(reader->array, TRUE); 
-    free(reader);
+    g_array_free(reader->array, TRUE);
+    MAL_GC_FREE(reader);
 }
 
 Reader *tokenize(char *line) {
@@ -82,11 +82,10 @@ char *replace_str(const char *str, const char *old, const char *new)
 {
     GRegex *reg = g_regex_new (old, 0, 0, NULL);
     char *str_tmp = g_regex_replace_literal(reg, str, -1, 0, new, 0, NULL);
-    free(reg);
+    MAL_GC_FREE(reg);
     return str_tmp;
 }
 
-
 MalVal *read_atom(Reader *reader) {
     char *token;
     GRegex *regex;
@@ -120,20 +119,21 @@ MalVal *read_atom(Reader *reader) {
         //g_print("read_atom string: %s\n", token);
         char *str_tmp = replace_str(g_match_info_fetch(matchInfo, 6), "\\\\\"", "\"");
         char *str_tmp2 = replace_str(str_tmp, "\\\\n", "\n");
-        free(str_tmp);
+        MAL_GC_FREE(str_tmp);
         char *str_tmp3 = replace_str(str_tmp2, "\\\\\\\\", "\\");
-        free(str_tmp2);
+        MAL_GC_FREE(str_tmp2);
         atom = malval_new_string(str_tmp3);
     } else if (g_match_info_fetch_pos(matchInfo, 7, &pos, NULL) && pos != -1) {
         //g_print("read_atom keyword\n");
-        atom = malval_new_keyword(g_match_info_fetch(matchInfo, 7));
+        atom = malval_new_keyword(MAL_GC_STRDUP(g_match_info_fetch(matchInfo, 7)));
     } else if (g_match_info_fetch_pos(matchInfo, 8, &pos, NULL) && pos != -1) {
         //g_print("read_atom symbol\n");
-        atom = malval_new_symbol(g_match_info_fetch(matchInfo, 8));
+        atom = malval_new_symbol(MAL_GC_STRDUP(g_match_info_fetch(matchInfo, 8)));
     } else {
         malval_free(atom);
         atom = NULL;
     }
+
     return atom;
 }
 

c/step0_repl.c

@@ -37,7 +37,7 @@ int main()
         ast = READ(prompt);
         if (!ast) return 0;
         exp = EVAL(ast, NULL);
-        g_print("%s\n", PRINT(exp));
+        puts(PRINT(exp));
  
         free(ast); // Free input string
     }

c/step1_read_print.c

@@ -21,7 +21,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -62,6 +62,8 @@ int main()
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt
     snprintf(prompt, sizeof(prompt), "user> ");
  
@@ -74,8 +76,8 @@ int main()
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step2_eval.c

@@ -24,7 +24,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -130,6 +130,8 @@ int main()
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env();
@@ -143,8 +145,8 @@ int main()
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step3_env.c

@@ -24,7 +24,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -156,6 +156,8 @@ int main()
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env();
@@ -169,8 +171,8 @@ int main()
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step4_if_fn_do.c

@@ -25,7 +25,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -195,6 +195,8 @@ int main()
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env();
@@ -208,8 +210,8 @@ int main()
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step5_tco.c

@@ -25,7 +25,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -208,6 +208,8 @@ int main()
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env();
@@ -221,8 +223,8 @@ int main()
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step6_file.c

@@ -25,7 +25,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -222,6 +222,8 @@ int main(int argc, char *argv[])
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env(argc, argv);
@@ -241,8 +243,8 @@ int main(int argc, char *argv[])
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step7_quote.c

@@ -25,7 +25,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -259,6 +259,8 @@ int main(int argc, char *argv[])
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env(argc, argv);
@@ -278,8 +280,8 @@ int main(int argc, char *argv[])
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step8_macros.c

@@ -26,7 +26,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -303,6 +303,8 @@ int main(int argc, char *argv[])
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env(argc, argv);
@@ -322,8 +324,8 @@ int main(int argc, char *argv[])
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/step9_try.c

@@ -27,7 +27,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -325,6 +325,8 @@ int main(int argc, char *argv[])
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env(argc, argv);
@@ -344,8 +346,8 @@ int main(int argc, char *argv[])
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/stepA_mal.c

@@ -27,7 +27,7 @@ MalVal *READ(char prompt[], char *str) {
         }
     }
     ast = read_str(line);
-    if (!str) { free(line); }
+    if (!str) { MAL_GC_FREE(line); }
     return ast;
 }
 
@@ -332,6 +332,8 @@ int main(int argc, char *argv[])
     char *output;
     char prompt[100];
 
+    MAL_GC_SETUP();
+
     // Set the initial prompt and environment
     snprintf(prompt, sizeof(prompt), "user> ");
     init_repl_env(argc, argv);
@@ -352,8 +354,8 @@ int main(int argc, char *argv[])
         output = PRINT(exp);
 
         if (output) { 
-            g_print("%s\n", output);
-            free(output);        // Free output string
+            puts(output);
+            MAL_GC_FREE(output);        // Free output string
         }
 
         //malval_free(exp);    // Free evaluated expression

c/types.c

@@ -5,6 +5,37 @@
 #include "types.h"
 #include "printer.h"
 
+#ifdef USE_GC
+void nop_free(void* ptr) {
+    (void)ptr; // Unused argument
+}
+
+static GMemVTable gc_gmem_vtable = {
+    .malloc = GC_malloc,
+    .realloc = GC_realloc,
+    .free = nop_free,
+    .calloc = NULL,
+    .try_malloc = NULL,
+    .try_realloc = NULL
+};
+
+void GC_setup() {
+    GC_INIT();
+    setenv("G_SLICE", "always-malloc", 1);
+    g_mem_gc_friendly = TRUE;
+    g_mem_set_vtable(&gc_gmem_vtable);
+}
+
+char* GC_strdup(const char *src) {
+    if (!src) {
+        return NULL;
+    }
+    char* dst = (char*)MAL_GC_MALLOC(strlen(src) + 1);
+    strcpy(dst, src);
+    return dst;
+}
+#endif
+
 
 // Errors/Exceptions
 
@@ -67,17 +98,16 @@ int _count(MalVal *obj) {
 
 // Allocate a malval and set its type and value
 MalVal *malval_new(MalType type, MalVal *metadata) {
-    MalVal *mv = (MalVal*)malloc(sizeof(MalVal));
+    MalVal *mv = (MalVal*)MAL_GC_MALLOC(sizeof(MalVal));
     mv->type = type;
     mv->metadata = metadata;
     return mv;
 }
 
-// 
 void malval_free(MalVal *mv) {
     // TODO: free collection items
     if (!(mv->type & (MAL_NIL|MAL_TRUE|MAL_FALSE))) {
-        free(mv);
+        MAL_GC_FREE(mv);
     }
 }
 

c/types.h

@@ -3,6 +3,24 @@
 
 #include <glib.h>
 
+#ifdef USE_GC
+
+#include <gc/gc.h>
+char* GC_strdup(const char *src);
+#define MAL_GC_SETUP()  GC_setup()
+#define MAL_GC_MALLOC   GC_MALLOC
+#define MAL_GC_FREE     nop_free
+#define MAL_GC_STRDUP   GC_strdup
+
+#else
+
+#include <string.h>
+#define MAL_GC_SETUP()
+#define MAL_GC_MALLOC   malloc
+#define MAL_GC_FREE     free
+#define MAL_GC_STRDUP   strdup
+
+#endif
 
 struct MalVal; // pre-declare