diff --git a/src/runtime/c/gu/defs.c b/src/runtime/c/gu/defs.c
index 2c3772b7c..5e78e797b 100644
--- a/src/runtime/c/gu/defs.c
+++ b/src/runtime/c/gu/defs.c
@@ -1,4 +1,4 @@
 #include <gu/defs.h>
 
 void* const gu_null = NULL;
-GuStruct* const gu_null_struct = NULL;
+GU_API_DATA GuStruct* const gu_null_struct = NULL;
diff --git a/src/runtime/c/gu/defs.h b/src/runtime/c/gu/defs.h
index 51a2293e3..f302481d6 100644
--- a/src/runtime/c/gu/defs.h
+++ b/src/runtime/c/gu/defs.h
@@ -25,6 +25,24 @@
 #ifndef GU_DEFS_H_
 #define GU_DEFS_H_
 
+// MSVC requires explicit export/import of
+// symbols in DLLs. CMake takes care of this
+// for functions, but not for data/variables.
+#if defined(_MSC_VER)
+#if defined(COMPILING_GU)
+#define GU_API_DATA_DECL __declspec(dllexport)
+#define GU_API_DATA __declspec(dllexport)
+#else
+#define GU_API_DATA_DECL __declspec(dllimport)
+#define GU_API_DATA ERROR_NOT_COMPILING_LIBGU
+#endif
+
+#else
+#define GU_API_DATA_DECL extern
+#define GU_API_DATA
+#endif
+// end MSVC workaround
+
 #include <stddef.h>
 #include <inttypes.h>
 #include <stdbool.h>
@@ -154,7 +172,7 @@ extern void* const gu_null;
 // Dummy struct used for generic struct pointers
 typedef struct GuStruct GuStruct;
 
-extern GuStruct* const gu_null_struct;
+GU_API_DATA_DECL GuStruct* const gu_null_struct;
 
 typedef uintptr_t GuWord;
 
diff --git a/src/runtime/c/gu/hash.c b/src/runtime/c/gu/hash.c
index 1666263e6..0057d0f42 100644
--- a/src/runtime/c/gu/hash.c
+++ b/src/runtime/c/gu/hash.c
@@ -25,7 +25,7 @@ gu_int_hash_fn(GuHasher* self, const void* p)
 	return (GuHash) *(const int*) p;
 }
 
-GuHasher gu_int_hasher[1] = {
+GU_API_DATA GuHasher gu_int_hasher[1] = {
 	{
 		{ gu_int_eq_fn },
 		gu_int_hash_fn
@@ -46,7 +46,7 @@ gu_addr_hash_fn(GuHasher* self, const void* p)
 	return (GuHash) (uintptr_t) p;
 }
 
-GuHasher gu_addr_hasher[1] = {
+GU_API_DATA GuHasher gu_addr_hasher[1] = {
 	{
 		{ gu_addr_eq_fn },
 		gu_addr_hash_fn
@@ -69,7 +69,7 @@ gu_word_hash_fn(GuHasher* self, const void* p)
 	return (GuHash) (uintptr_t) p;
 }
 
-GuHasher gu_word_hasher[1] = {
+GU_API_DATA GuHasher gu_word_hasher[1] = {
 	{
 		{ gu_word_eq_fn },
 		gu_word_hash_fn
diff --git a/src/runtime/c/gu/hash.h b/src/runtime/c/gu/hash.h
index e16c2f454..da612f3f4 100644
--- a/src/runtime/c/gu/hash.h
+++ b/src/runtime/c/gu/hash.h
@@ -31,10 +31,10 @@ struct GuHasher {
 };
 
 
-extern GuHasher gu_int_hasher[1];
+GU_API_DATA GuHasher gu_int_hasher[1];
 
-extern GuHasher gu_addr_hasher[1];
+GU_API_DATA GuHasher gu_addr_hasher[1];
 
-extern GuHasher gu_word_hasher[1];
+GU_API_DATA GuHasher gu_word_hasher[1];
 
 #endif // GU_HASH_H_
diff --git a/src/runtime/c/gu/mem.c b/src/runtime/c/gu/mem.c
index 0fc315a4f..325eaea77 100644
--- a/src/runtime/c/gu/mem.c
+++ b/src/runtime/c/gu/mem.c
@@ -8,7 +8,9 @@
 #include <sys/mman.h>
 #include <sys/stat.h>
 #endif
+#if !defined(_MSC_VER)
 #include <unistd.h>
+#endif
 #include <fcntl.h>
 
 #ifdef USE_VALGRIND
diff --git a/src/runtime/c/gu/seq.c b/src/runtime/c/gu/seq.c
index 88b762a04..8cf55929b 100644
--- a/src/runtime/c/gu/seq.c
+++ b/src/runtime/c/gu/seq.c
@@ -3,7 +3,7 @@
 #include <gu/fun.h>
 #include <gu/assert.h>
 #include <stdlib.h>
-#ifdef __MINGW32__
+#if defined(__MINGW32__) || defined(_MSC_VER)
 #include <malloc.h>
 #endif
 
diff --git a/src/runtime/c/gu/string.c b/src/runtime/c/gu/string.c
index 5a31c8806..3e754a72c 100644
--- a/src/runtime/c/gu/string.c
+++ b/src/runtime/c/gu/string.c
@@ -5,7 +5,7 @@
 #include <gu/utf8.h>
 #include <gu/assert.h>
 #include <stdlib.h>
-#ifdef __MINGW32__
+#if defined(__MINGW32__) || defined(_MSC_VER)
 #include <malloc.h>
 #endif
 
@@ -273,7 +273,7 @@ gu_string_eq_fn(GuEquality* self, const void* p1, const void* p2)
 	return strcmp((GuString) p1, (GuString) p2) == 0;
 }
 
-GuEquality gu_string_equality[1] = { { gu_string_eq_fn } };
+GU_API_DATA GuEquality gu_string_equality[1] = { { gu_string_eq_fn } };
 
 static int
 gu_string_cmp_fn(GuOrder* self, const void* p1, const void* p2)
@@ -282,7 +282,7 @@ gu_string_cmp_fn(GuOrder* self, const void* p1, const void* p2)
 	return strcmp((GuString) p1, (GuString) p2);
 }
 
-GuOrder gu_string_order[1] = { { gu_string_cmp_fn } };
+GU_API_DATA GuOrder gu_string_order[1] = { { gu_string_cmp_fn } };
 
 static GuHash
 gu_string_hasher_hash(GuHasher* self, const void* p)
@@ -291,7 +291,7 @@ gu_string_hasher_hash(GuHasher* self, const void* p)
 	return gu_string_hash(0, (GuString) p);
 }
 
-GuHasher gu_string_hasher[1] = {
+GU_API_DATA GuHasher gu_string_hasher[1] = {
 	{
 		.eq = { gu_string_eq_fn },
 		.hash = gu_string_hasher_hash
diff --git a/src/runtime/c/gu/string.h b/src/runtime/c/gu/string.h
index 4064286a9..2bf1aef45 100644
--- a/src/runtime/c/gu/string.h
+++ b/src/runtime/c/gu/string.h
@@ -58,9 +58,9 @@ gu_string_is_prefix(GuString s1, GuString s2);
 
 #if defined(GU_FUN_H_) && !defined(GU_STRING_H_FUN_)
 #define GU_STRING_H_FUN_
-extern GuEquality gu_string_equality[1];
+GU_API_DATA GuEquality gu_string_equality[1];
 
-extern GuOrder gu_string_order[1];
+GU_API_DATA GuOrder gu_string_order[1];
 #endif
 
 #if defined(GU_HASH_H_) && !defined(GU_STRING_H_HASH_)
@@ -69,7 +69,7 @@ extern GuOrder gu_string_order[1];
 GuHash
 gu_string_hash(GuHash h, GuString s);
 
-extern GuHasher gu_string_hasher[1];
+GU_API_DATA GuHasher gu_string_hasher[1];
 #endif
 
 #if defined(GU_SEQ_H_) && !defined(GU_STRING_H_SEQ_)
diff --git a/src/runtime/c/gu/variant.c b/src/runtime/c/gu/variant.c
index dd4149429..75b75c086 100644
--- a/src/runtime/c/gu/variant.c
+++ b/src/runtime/c/gu/variant.c
@@ -108,4 +108,4 @@ gu_variant_intval(GuVariant variant)
 	return (variant / GU_VARIANT_ALIGNMENT);
 }
 
-const GuVariant gu_null_variant = { (GuWord) NULL };
+GU_API_DATA const GuVariant gu_null_variant = { (GuWord) NULL };
diff --git a/src/runtime/c/gu/variant.h b/src/runtime/c/gu/variant.h
index a4c24b4af..8e7741694 100644
--- a/src/runtime/c/gu/variant.h
+++ b/src/runtime/c/gu/variant.h
@@ -97,7 +97,7 @@ gu_variant_from_ptr(const void* p)
 	return (uintptr_t) p;
 }
 
-extern const GuVariant gu_null_variant;
+GU_API_DATA const GuVariant gu_null_variant;
 
 static inline bool
 gu_variant_is_null(GuVariant v) {
diff --git a/src/runtime/c/pgf/data.h b/src/runtime/c/pgf/data.h
index 5b1842d74..3941580cb 100644
--- a/src/runtime/c/pgf/data.h
+++ b/src/runtime/c/pgf/data.h
@@ -56,7 +56,7 @@ typedef struct {
 	PgfPatt patt;
 } PgfPattAs;
 
-typedef void PgfPattWild;
+typedef char PgfPattWild;
 
 typedef struct {
 	PgfPatt patt;
@@ -241,12 +241,15 @@ typedef struct PgfSymbolKP
 } PgfSymbolKP;
 
 typedef struct {
+	char nothing[0]; // Empty struct
 } PgfSymbolNE;
 
 typedef struct {
+	char nothing[0]; // Empty struct
 } PgfSymbolBIND;
 
 typedef struct {
+	char nothing[0]; // Empty struct
 } PgfSymbolCAPIT;
 
 typedef GuBuf PgfProductionIdx;
diff --git a/src/runtime/c/pgf/evaluator.c b/src/runtime/c/pgf/evaluator.c
index 457f60896..698601820 100644
--- a/src/runtime/c/pgf/evaluator.c
+++ b/src/runtime/c/pgf/evaluator.c
@@ -437,7 +437,7 @@ pgf_evaluate_accum_init_flt(PgfReasoner* rs,
 					   rs->pool);
 	lit_flt->val = val;
 	accum->enter_stack_ptr = rs->enter_stack_ptr;
-	rs->enter_stack_ptr = ((void*)accum)-sizeof(void*)*2;
+	rs->enter_stack_ptr = ((char*)accum)-sizeof(char*)*2;
 	accum->consts = NULL;
 }
 
diff --git a/src/runtime/c/pgf/jit.c b/src/runtime/c/pgf/jit.c
index 4fe18d181..003fa2630 100644
--- a/src/runtime/c/pgf/jit.c
+++ b/src/runtime/c/pgf/jit.c
@@ -5,7 +5,7 @@
 #include <pgf/reasoner.h>
 #include <pgf/reader.h>
 #include "lightning.h"
-#ifdef __MINGW32__
+#if defined(__MINGW32__) || defined(_MSC_VER)
 #include <malloc.h>
 #endif
 
@@ -43,7 +43,7 @@ typedef struct {
 #define JIT_VSTATE JIT_V1
 #define JIT_VCLOS  JIT_V2
 
-#if defined(__MINGW32__)
+#if defined(__MINGW32__) || defined(_MSC_VER)
 #include <windows.h>
 
 static int
@@ -71,7 +71,7 @@ pgf_jit_alloc_page(PgfReader* rdr)
 
 #if defined(ANDROID)
 	if ((page = memalign(page_size, page_size)) == NULL) {	
-#elif defined(__MINGW32__)
+#elif defined(__MINGW32__) || defined(_MSC_VER)
 	if ((page = malloc(page_size)) == NULL) {
 #else
 	if (posix_memalign(&page, page_size, page_size) != 0) {
diff --git a/src/runtime/c/pgf/linearizer.h b/src/runtime/c/pgf/linearizer.h
index 8178facdb..08ebfd159 100644
--- a/src/runtime/c/pgf/linearizer.h
+++ b/src/runtime/c/pgf/linearizer.h
@@ -29,6 +29,7 @@ PgfCncTreeEnum*
 pgf_lzr_concretize(PgfConcr* concr, PgfExpr expr, GuExn* err, GuPool* pool);
 
 typedef struct {
+	char nothing[0]; // Empty struct
 } PgfLinNonExist;
 
 PgfCncTree
diff --git a/src/runtime/c/pgf/literals.c b/src/runtime/c/pgf/literals.c
index ac57b150f..b5332b1ec 100644
--- a/src/runtime/c/pgf/literals.c
+++ b/src/runtime/c/pgf/literals.c
@@ -334,7 +334,7 @@ pgf_match_name_lit(PgfLiteralCallback* self, PgfConcr* concr,
 	return ep;
 }
 
-PgfLiteralCallback pgf_nerc_literal_callback =
+PGF_API_DATA PgfLiteralCallback pgf_nerc_literal_callback =
   { pgf_match_name_lit, pgf_predict_empty } ;
 
 static void
@@ -419,7 +419,7 @@ pgf_match_unknown_lit(PgfLiteralCallback* self, PgfConcr* concr,
 	return ep;
 }
 
-PgfLiteralCallback pgf_unknown_literal_callback =
+PGF_API_DATA PgfLiteralCallback pgf_unknown_literal_callback =
   { pgf_match_unknown_lit, pgf_predict_empty } ;
 
 PgfCallbacksMap*
diff --git a/src/runtime/c/pgf/literals.h b/src/runtime/c/pgf/literals.h
index 7de17b121..624d82f9f 100644
--- a/src/runtime/c/pgf/literals.h
+++ b/src/runtime/c/pgf/literals.h
@@ -1,13 +1,33 @@
 #ifndef PGF_LITERALS_H_
 #define PGF_LITERALS_H_
 
+// MSVC requires explicit export/import of
+// symbols in DLLs. CMake takes care of this
+// for functions, but not for data/variables.
+#if defined(_MSC_VER)
+#if defined(COMPILING_PGF)
+#define PGF_API_DATA_DECL __declspec(dllexport)
+#define PGF_API_DATA __declspec(dllexport)
+#else
+#define PGF_API_DATA_DECL __declspec(dllimport)
+#define PGF_API_DATA ERROR_NOT_COMPILING_LIBPGF
+#endif
+
+#else
+
+#define PGF_API_DATA_DECL extern
+#define PGF_API_DATA
+#endif
+// end MSVC workaround
+ 
+ 
 #include <pgf/data.h>
 
 // literal for named entities recognition
-extern PgfLiteralCallback pgf_nerc_literal_callback;
+PGF_API_DATA_DECL PgfLiteralCallback pgf_nerc_literal_callback;
 
 // literal for finding unknown words
-extern PgfLiteralCallback pgf_unknown_literal_callback;
+PGF_API_DATA_DECL PgfLiteralCallback pgf_unknown_literal_callback;
 
 PgfCCat*
 pgf_literal_cat(PgfConcr* concr, PgfLiteral lit);
diff --git a/src/runtime/c/pgf/reader.c b/src/runtime/c/pgf/reader.c
index cb690a353..5d509220a 100644
--- a/src/runtime/c/pgf/reader.c
+++ b/src/runtime/c/pgf/reader.c
@@ -14,7 +14,7 @@
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
-#ifdef __MINGW32__
+#if defined(__MINGW32__) || defined(_MSC_VER)
 #include <malloc.h>
 #endif