gdb

(gdb) run t4.rb
Starting program: /home/yumiyama/work/mruby/mruby/bin/mruby t4.rb
t4.rb:6: expected String (TypeError)
"done."

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff77f1201 in EVP_MD_CTX_cleanup () from /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
(gdb) bt
#0  0x00007ffff77f1201 in EVP_MD_CTX_cleanup () from /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
#1  0x00007ffff777265d in HMAC_CTX_cleanup () from /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
#2  0x000000000045280c in lib_hmac_free (mrb=0x6ab010, ptr=0x0) at build/mrbgems/mruby-digest//src/digest.c:111
#3  0x000000000041d41b in obj_free (mrb=0x6ab010, obj=0x744140) at /home/yumiyama/work/mruby/mruby/src/gc.c:601
#4  0x000000000041e212 in mrb_free_heap (mrb=0x6ab010) at /home/yumiyama/work/mruby/mruby/src/gc.c:325
#5  0x000000000040491f in mrb_close (mrb=0x6ab010) at /home/yumiyama/work/mruby/mruby/src/state.c:150
#6  0x0000000000403fca in main (argc=<optimized out>, argv=<optimized out>) at /home/yumiyama/work/mruby/mruby/mrbgems/mruby-bin-mruby//tools/mruby/mruby.c:243
(gdb)

mruby-digest.patch

diff --git a/src/digest.c b/src/digest.c
index cc628ea..0e483f1 100644
--- a/src/digest.c
+++ b/src/digest.c
@@ -577,6 +577,9 @@ mrb_digest_init(mrb_state *mrb, mrb_value self)
   struct mrb_md *md;
   mrb_value t;

+  DATA_TYPE(self) = &mrb_md_type;
+  DATA_PTR(self) = NULL;
+
   c = mrb_obj_class(mrb, self);
   if (!mrb_const_defined(mrb, mrb_obj_value(c), mrb_intern(mrb, TYPESYM))) {
     mrb_raise(mrb, E_NOTIMP_ERROR, "Digest::Base is an abstract class");
@@ -596,7 +599,6 @@ mrb_digest_init(mrb_state *mrb, mrb_value self)
   md = (struct mrb_md *)mrb_malloc(mrb, sizeof(*md));
   lib_md_init(mrb, md, mrb_fixnum(t));
   DATA_PTR(self) = md;
-  DATA_TYPE(self) = &mrb_md_type;
   return self;
 }

@@ -690,6 +692,9 @@ mrb_hmac_init(mrb_state *mrb, mrb_value self)
   int keylen;
   char *key;

+  DATA_TYPE(self) = &mrb_hmac_type;
+  DATA_PTR(self) = NULL;
+
   mrb_get_args(mrb, "so", &key, &keylen, &digest);
   t = mrb_const_get(mrb, digest, mrb_intern(mrb, TYPESYM));
   if (mrb_nil_p(t)) {
@@ -704,7 +709,6 @@ mrb_hmac_init(mrb_state *mrb, mrb_value self)
   hmac = (struct mrb_hmac *)mrb_malloc(mrb, sizeof(*hmac));
   lib_hmac_init(mrb, hmac, mrb_fixnum(t), (unsigned char *)key, keylen);
   DATA_PTR(self) = hmac;
-  DATA_TYPE(self) = &mrb_hmac_type;
   return self;
 }

t4.rb

if Object.const_defined?(:RUBY_VERSION)
    require 'digest/hmac'
end

begin
  Digest::HMAC.hexdigest('data', nil, Digest::SHA256)
rescue => e
  p e
end
p 'done.'