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Eliminate a wrong -Wmaybe-uninitialized warning in GCC #136

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Jul 14, 2021
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Eliminate a wrong -Wmaybe-uninitialized warning in GCC #136

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14 changes: 12 additions & 2 deletions src/modules/rangeproof/main_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -182,7 +182,15 @@ int secp256k1_pedersen_blind_generator_blind_sum(const secp256k1_context* ctx, c
}

secp256k1_scalar_set_int(&sum, 0);
for (i = 0; i < n_total; i++) {

/* Here, n_total > 0. Thus the loop runs at least once.
Thus we may use a do-while loop, which checks the loop
condition only at the end.

The do-while loop helps GCC prove that the loop runs at least
once and suppresses a -Wmaybe-uninitialized warning. */
i = 0;
do {
int overflow = 0;
secp256k1_scalar addend;
secp256k1_scalar_set_u64(&addend, value[i]); /* s = v */
Expand All @@ -207,7 +215,9 @@ int secp256k1_pedersen_blind_generator_blind_sum(const secp256k1_context* ctx, c
secp256k1_scalar_cond_negate(&addend, i < n_inputs); /* s is negated if it's an input */
secp256k1_scalar_add(&sum, &sum, &addend); /* sum += s */
secp256k1_scalar_clear(&addend);
}

i++;
} while (i < n_total);

/* Right now tmp has the last pedersen blinding factor. Subtract the sum from it. */
secp256k1_scalar_negate(&sum, &sum);
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