Shush some dead assignments.

Appease clang scan-build a bit. I'm not sure it's actually worth silencing all
of them because some of them look like preserving invariants between local
variables, but some are clearly pointless or can be restructured slightly.

Change-Id: I0bc81e2589bb402ff3ef0182d7a8921e31b85052
Reviewed-on: https://boringssl-review.googlesource.com/2205
Reviewed-by: Adam Langley <agl@google.com>

crypto/asn1/tasn_dec.c

@@ -599,14 +599,13 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
 	{
 	int flags, aclass;
 	int ret;
-	const unsigned char *p, *q;
+	const unsigned char *p;
 	if (!val)
 		return 0;
 	flags = tt->flags;
 	aclass = flags & ASN1_TFLG_TAG_CLASS;
 
 	p = *in;
-	q = p;
 
 	if (flags & ASN1_TFLG_SK_MASK)
 		{
@@ -663,7 +662,7 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
 		while(len > 0)
 			{
 			ASN1_VALUE *skfield;
-			q = p;
+			const unsigned char *q = p;
 			/* See if EOC found */
 			if (asn1_check_eoc(&p, len))
 				{

crypto/bn/exponentiation.c

@@ -416,7 +416,7 @@ err:
 
 static int mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
                         const BIGNUM *m, BN_CTX *ctx) {
-  int i, j, bits, ret = 0, wstart, wend, window, wvalue;
+  int i, j, bits, ret = 0, wstart, window;
   int start = 1;
   BIGNUM *aa;
   /* Table of variables obtained from 'ctx' */
@@ -485,15 +485,16 @@ static int mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
   start = 1; /* This is used to avoid multiplication etc
               * when there is only the value '1' in the
               * buffer. */
-  wvalue = 0;        /* The 'value' of the window */
   wstart = bits - 1; /* The top bit of the window */
-  wend = 0;          /* The bottom bit of the window */
 
   if (!BN_one(r)) {
     goto err;
   }
 
   for (;;) {
+    int wvalue; /* The 'value' of the window */
+    int wend; /* The bottom bit of the window */
+
     if (BN_is_bit_set(p, wstart) == 0) {
       if (!start) {
         if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx)) {
@@ -542,7 +543,6 @@ static int mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 
     /* move the 'window' down further */
     wstart -= wend + 1;
-    wvalue = 0;
     start = 0;
     if (wstart < 0) {
       break;
@@ -601,7 +601,7 @@ int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
 
 int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
                     const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) {
-  int i, j, bits, ret = 0, wstart, wend, window, wvalue;
+  int i, j, bits, ret = 0, wstart, window;
   int start = 1;
   BIGNUM *d, *r;
   const BIGNUM *aa;
@@ -680,9 +680,7 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
   start = 1; /* This is used to avoid multiplication etc
               * when there is only the value '1' in the
               * buffer. */
-  wvalue = 0;        /* The 'value' of the window */
   wstart = bits - 1; /* The top bit of the window */
-  wend = 0;          /* The bottom bit of the window */
 
   j = m->top; /* borrow j */
   if (m->d[j - 1] & (((BN_ULONG)1) << (BN_BITS2 - 1))) {
@@ -701,6 +699,9 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
   }
 
   for (;;) {
+    int wvalue; /* The 'value' of the window */
+    int wend; /* The bottom bit of the window */
+
     if (BN_is_bit_set(p, wstart) == 0) {
       if (!start) {
         if (!BN_mod_mul_montgomery(r, r, r, mont, ctx))
@@ -716,7 +717,6 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
     /* We now have wstart on a 'set' bit, we now need to work out how bit a
      * window to do.  To do this we need to scan forward until the last set bit
      * before the end of the window */
-    j = wstart;
     wvalue = 1;
     wend = 0;
     for (i = 1; i < window; i++) {
@@ -748,7 +748,6 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
 
     /* move the 'window' down further */
     wstart -= wend + 1;
-    wvalue = 0;
     start = 0;
     if (wstart < 0) {
       break;

crypto/cipher/e_rc2.c

@@ -279,7 +279,6 @@ static void RC2_cbc_encrypt(const uint8_t *in, uint8_t *out, size_t length,
     l2c(xor0, iv);
     l2c(xor1, iv);
   }
-  tin0 = tin1 = tout0 = tout1 = xor0 = xor1 = 0;
   tin[0] = tin[1] = 0;
 }
 

crypto/ec/wnaf.c

@@ -443,8 +443,8 @@ int ec_wNAF_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
          * as the wNAF belonging to the generator,
          * so wNAF splitting will not buy us anything. */
 
-        numblocks = 1;
+        numblocks = 1; /* don't use wNAF splitting */
-        totalnum = num + 1; /* don't use wNAF splitting */
+        totalnum = num + numblocks;
         wNAF[num] = tmp_wNAF;
         wNAF[num + 1] = NULL;
         wNAF_len[num] = tmp_len;

crypto/x509/t_crl.c

@@ -91,7 +91,6 @@ int X509_CRL_print(BIO *out, X509_CRL *x)
 	BIO_printf(out, "Certificate Revocation List (CRL):\n");
 	l = X509_CRL_get_version(x);
 	BIO_printf(out, "%8sVersion %lu (0x%lx)\n", "", l+1, l);
-	i = OBJ_obj2nid(x->sig_alg->algorithm);
 	X509_signature_print(out, x->sig_alg, NULL);
 	p=X509_NAME_oneline(X509_CRL_get_issuer(x),NULL,0);
 	BIO_printf(out,"%8sIssuer: %s\n","",p);