Refactor _yr_atoms_extract_from_re_node.

This function was refactored from and converted from recursive to iterative, using a stack.

Makefile.am

@@ -44,6 +44,8 @@ test_bitmask_SOURCES = tests/test-bitmask.c
 test_bitmask_LDADD = libyara/.libs/libyara.a
 test_math_SOURCES = tests/test-math.c tests/util.c
 test_math_LDADD = libyara/.libs/libyara.a
+test_stack_SOURCES = tests/test-stack.c
+test_stack_LDADD = libyara/.libs/libyara.a
 
 TESTS = $(check_PROGRAMS)
 TESTS_ENVIRONMENT = TOP_SRCDIR=$(top_srcdir)
@@ -56,7 +58,8 @@ check_PROGRAMS = test-alignment \
   test-elf \
   test-version \
   test-bitmask \
-  test-math
+  test-math \
+  test-stack
 
 if POSIX
 # The -fsanitize=address option makes test-exception fail. Include the test

libyara/Makefile.am

@@ -89,6 +89,7 @@ yarainclude_HEADERS = \
   include/yara/scan.h \
   include/yara/scanner.h \
   include/yara/sizedstr.h \
+  include/yara/stack.h \
   include/yara/stopwatch.h \
   include/yara/stream.h \
   include/yara/strutils.h \
@@ -152,6 +153,7 @@ libyara_la_SOURCES = \
   scan.c \
   scanner.c \
   sizedstr.c \
+  stack.c \
   stopwatch.c \
   strutils.c \
   stream.c \