Merge bitcoin#607: Use size_t shifts when computing a size_t

e6d01e9 Use size_t shifts when computing a size_t (Pieter Wuille)

Pull request description:

  This was detected by compiling with MSVC; it triggers warning C4334.

  I don't think this is necessary, as we know the maximum shift is a very small integer, but this makes the code more obviously correct.

Tree-SHA512: 3c0cf412c75b4361d01e78bf13fe81c3f28b82abd40b0706285cc691124381cb1ff1f1c3512420250180b7612a471ce48357b282b1e34a08f5359e58af25e198

src/ecmult_impl.h

@@ -960,7 +960,7 @@ static size_t secp256k1_pippenger_scratch_size(size_t n_points, int bucket_windo
     size_t entries = n_points + 1;
 #endif
     size_t entry_size = sizeof(secp256k1_ge) + sizeof(secp256k1_scalar) + sizeof(struct secp256k1_pippenger_point_state) + (WNAF_SIZE(bucket_window+1)+1)*sizeof(int);
-    return ((1<<bucket_window) * sizeof(secp256k1_gej) + sizeof(struct secp256k1_pippenger_state) + entries * entry_size);
+    return (sizeof(secp256k1_gej) << bucket_window) + sizeof(struct secp256k1_pippenger_state) + entries * entry_size;
 }
 
 static int secp256k1_ecmult_pippenger_batch(const secp256k1_ecmult_context *ctx, secp256k1_scratch *scratch, secp256k1_gej *r, const secp256k1_scalar *inp_g_sc, secp256k1_ecmult_multi_callback cb, void *cbdata, size_t n_points, size_t cb_offset) {
@@ -996,7 +996,7 @@ static int secp256k1_ecmult_pippenger_batch(const secp256k1_ecmult_context *ctx,
     state_space = (struct secp256k1_pippenger_state *) secp256k1_scratch_alloc(scratch, sizeof(*state_space));
     state_space->ps = (struct secp256k1_pippenger_point_state *) secp256k1_scratch_alloc(scratch, entries * sizeof(*state_space->ps));
     state_space->wnaf_na = (int *) secp256k1_scratch_alloc(scratch, entries*(WNAF_SIZE(bucket_window+1)) * sizeof(int));
-    buckets = (secp256k1_gej *) secp256k1_scratch_alloc(scratch, (1<<bucket_window) * sizeof(*buckets));
+    buckets = (secp256k1_gej *) secp256k1_scratch_alloc(scratch, sizeof(*buckets) << bucket_window);
 
     if (inp_g_sc != NULL) {
         scalars[0] = *inp_g_sc;
@@ -1063,7 +1063,7 @@ static size_t secp256k1_pippenger_max_points(secp256k1_scratch *scratch) {
 #ifdef USE_ENDOMORPHISM
         entry_size = 2*entry_size;
 #endif
-        space_overhead = ((1<<bucket_window) * sizeof(secp256k1_gej) + entry_size + sizeof(struct secp256k1_pippenger_state));
+        space_overhead = (sizeof(secp256k1_gej) << bucket_window) + entry_size + sizeof(struct secp256k1_pippenger_state);
         if (space_overhead > max_alloc) {
             break;
         }