For MSVC use alloca() instead of VLA

ref/haraka.c

@@ -12,6 +12,7 @@
 #include <stdlib.h>
 
 #include "haraka.h"
+#include "utils.h"
 
 #define HARAKAS_RATE 32
 
@@ -696,7 +697,7 @@ static void haraka_S_absorb(unsigned char *s, unsigned int r,
                             unsigned char p, const spx_ctx *ctx)
 {
     unsigned long long i;
-    unsigned char t[r];
+    SPX_VLA(uint8_t, t, r);
 
     while (mlen >= r) {
         /* XOR block to state */

ref/sha2.c

@@ -627,7 +627,7 @@ void sha512(uint8_t *out, const uint8_t *in, size_t inlen) {
 void mgf1_256(unsigned char *out, unsigned long outlen,
           const unsigned char *in, unsigned long inlen)
 {
-    unsigned char inbuf[inlen + 4];
+    SPX_VLA(uint8_t, inbuf, inlen+4);
     unsigned char outbuf[SPX_SHA256_OUTPUT_BYTES];
     unsigned long i;
 
@@ -653,7 +653,7 @@ void mgf1_256(unsigned char *out, unsigned long outlen,
 void mgf1_512(unsigned char *out, unsigned long outlen,
           const unsigned char *in, unsigned long inlen)
 {
-    unsigned char inbuf[inlen + 4];
+    SPX_VLA(uint8_t, inbuf, inlen+4);
     unsigned char outbuf[SPX_SHA512_OUTPUT_BYTES];
     unsigned long i;
 

ref/thash_haraka_robust.c

@@ -4,6 +4,7 @@
 #include "thash.h"
 #include "address.h"
 #include "params.h"
+#include "utils.h"
 
 #include "haraka.h"
 
@@ -13,8 +14,8 @@
 void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
            const spx_ctx *ctx, uint32_t addr[8])
 {
-    unsigned char buf[SPX_ADDR_BYTES + inblocks*SPX_N];
-    unsigned char bitmask[inblocks * SPX_N];
+    SPX_VLA(uint8_t, buf, SPX_ADDR_BYTES + inblocks*SPX_N);
+    SPX_VLA(uint8_t, bitmask, inblocks*SPX_N);
     unsigned char outbuf[32];
     unsigned char buf_tmp[64];
     unsigned int i;

ref/thash_haraka_simple.c

@@ -4,6 +4,7 @@
 #include "thash.h"
 #include "address.h"
 #include "params.h"
+#include "utils.h"
 
 #include "haraka.h"
 
@@ -13,7 +14,7 @@
 void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
            const spx_ctx *ctx, uint32_t addr[8])
 {
-    unsigned char buf[SPX_ADDR_BYTES + inblocks*SPX_N];
+    SPX_VLA(uint8_t, buf, SPX_ADDR_BYTES + inblocks*SPX_N);
     unsigned char outbuf[32];
     unsigned char buf_tmp[64];
 

ref/thash_sha2_robust.c

@@ -4,6 +4,7 @@
 #include "thash.h"
 #include "address.h"
 #include "params.h"
+#include "utils.h"
 #include "sha2.h"
 
 #if SPX_SHA512
@@ -23,9 +24,9 @@ void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
         return;
     }
 #endif
-    unsigned char buf[SPX_N + SPX_SHA256_ADDR_BYTES + inblocks*SPX_N];
     unsigned char outbuf[SPX_SHA256_OUTPUT_BYTES];
-    unsigned char bitmask[inblocks * SPX_N];
+    SPX_VLA(uint8_t, bitmask, inblocks * SPX_N);
+    SPX_VLA(uint8_t, buf, SPX_N + SPX_SHA256_OUTPUT_BYTES + inblocks*SPX_N);
     uint8_t sha2_state[40];
     unsigned int i;
 
@@ -49,9 +50,9 @@ void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
 static void thash_512(unsigned char *out, const unsigned char *in, unsigned int inblocks,
            const spx_ctx *ctx, uint32_t addr[8])
 {
-    unsigned char buf[SPX_N + SPX_SHA256_ADDR_BYTES + inblocks*SPX_N];
     unsigned char outbuf[SPX_SHA512_OUTPUT_BYTES];
-    unsigned char bitmask[inblocks * SPX_N];
+    SPX_VLA(uint8_t, bitmask, inblocks * SPX_N);
+    SPX_VLA(uint8_t, buf, SPX_N + SPX_SHA256_ADDR_BYTES + inblocks*SPX_N);
     uint8_t sha2_state[72];
     unsigned int i;
 

ref/thash_sha2_simple.c

@@ -4,6 +4,7 @@
 #include "thash.h"
 #include "address.h"
 #include "params.h"
+#include "utils.h"
 #include "sha2.h"
 
 #if SPX_SHA512
@@ -24,9 +25,9 @@ void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
     }
 #endif
 
-    unsigned char buf[SPX_SHA256_ADDR_BYTES + inblocks*SPX_N];
     unsigned char outbuf[SPX_SHA256_OUTPUT_BYTES];
     uint8_t sha2_state[40];
+    SPX_VLA(uint8_t, buf, SPX_SHA256_ADDR_BYTES + inblocks*SPX_N);
 
     /* Retrieve precomputed state containing pub_seed */
     memcpy(sha2_state, ctx->state_seeded, 40 * sizeof(uint8_t));
@@ -42,9 +43,9 @@ void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
 static void thash_512(unsigned char *out, const unsigned char *in, unsigned int inblocks,
            const spx_ctx *ctx, uint32_t addr[8])
 {
-    unsigned char buf[SPX_SHA256_ADDR_BYTES + inblocks*SPX_N];
     unsigned char outbuf[SPX_SHA512_OUTPUT_BYTES];
     uint8_t sha2_state[72];
+    SPX_VLA(uint8_t, buf, SPX_SHA256_ADDR_BYTES + inblocks*SPX_N);
 
     /* Retrieve precomputed state containing pub_seed */
     memcpy(sha2_state, ctx->state_seeded_512, 72 * sizeof(uint8_t));

ref/thash_shake_robust.c

@@ -4,6 +4,7 @@
 #include "thash.h"
 #include "address.h"
 #include "params.h"
+#include "utils.h"
 
 #include "fips202.h"
 
@@ -13,8 +14,8 @@
 void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
            const spx_ctx *ctx, uint32_t addr[8])
 {
-    unsigned char buf[SPX_N + SPX_ADDR_BYTES + inblocks*SPX_N];
-    unsigned char bitmask[inblocks * SPX_N];
+    SPX_VLA(uint8_t, buf, SPX_N + SPX_ADDR_BYTES + inblocks*SPX_N);
+    SPX_VLA(uint8_t, bitmask, inblocks * SPX_N);
     unsigned int i;
 
     memcpy(buf, ctx->pub_seed, SPX_N);

ref/thash_shake_simple.c

@@ -4,6 +4,7 @@
 #include "thash.h"
 #include "address.h"
 #include "params.h"
+#include "utils.h"
 
 #include "fips202.h"
 
@@ -13,7 +14,7 @@
 void thash(unsigned char *out, const unsigned char *in, unsigned int inblocks,
            const spx_ctx *ctx, uint32_t addr[8])
 {
-    unsigned char buf[SPX_N + SPX_ADDR_BYTES + inblocks*SPX_N];
+    SPX_VLA(uint8_t, buf, SPX_N + SPX_ADDR_BYTES + inblocks*SPX_N);
 
     memcpy(buf, ctx->pub_seed, SPX_N);
     memcpy(buf + SPX_N, addr, SPX_ADDR_BYTES);

ref/utils.c

@@ -110,8 +110,8 @@ void treehash(unsigned char *root, unsigned char *auth_path, const spx_ctx* ctx,
                  uint32_t /* addr_idx */, const uint32_t[8] /* tree_addr */),
               uint32_t tree_addr[8])
 {
-    unsigned char stack[(tree_height + 1)*SPX_N];
-    unsigned int heights[tree_height + 1];
+    SPX_VLA(uint8_t, stack, (tree_height+1)*SPX_N);
+    SPX_VLA(unsigned int, heights, tree_height+1);
     unsigned int offset = 0;
     uint32_t idx;
     uint32_t tree_idx;

ref/utils.h

@@ -6,6 +6,17 @@
 #include "context.h"
 
 
+/* To support MSVC use alloca() instead of VLAs. See #20. */
+#ifdef _MSC_VER
+/* MSVC defines _alloca in malloc.h */
+# include <malloc.h>
+/* Note: _malloca(), which is recommended over deprecated _alloca,
+   requires that you call _freea(). So we stick with _alloca */ 
+# define SPX_VLA(__t,__x,__s) __t *__x = (__t*)_alloca((__s)*sizeof(__t))
+#else
+# define SPX_VLA(__t,__x,__s) __t __x[__s]
+#endif
+
 /**
  * Converts the value of 'in' to 'outlen' bytes in big-endian byte order.
  */
@@ -44,4 +55,5 @@ void treehash(unsigned char *root, unsigned char *auth_path,
                  uint32_t /* addr_idx */, const uint32_t[8] /* tree_addr */),
               uint32_t tree_addr[8]);
 
+
 #endif

ref/utilsx1.c

@@ -32,7 +32,7 @@ void treehashx1(unsigned char *root, unsigned char *auth_path,
                 void *info)
 {
     /* This is where we keep the intermediate nodes */
-    unsigned char stack[tree_height*SPX_N];
+    SPX_VLA(uint8_t, stack, tree_height*SPX_N);
 
     uint32_t idx;
     uint32_t max_idx = (1 << tree_height) - 1;