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Avoid memset for struct initialization#2051

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tatsuhiro-t merged 1 commit intomainfrom
avoid-memset
Mar 3, 2026
Merged

Avoid memset for struct initialization#2051
tatsuhiro-t merged 1 commit intomainfrom
avoid-memset

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@tatsuhiro-t tatsuhiro-t commented Mar 3, 2026

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@tatsuhiro-t tatsuhiro-t added this to the v1.22.0 milestone Mar 3, 2026
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Summary of Changes

Hello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the initialization patterns for various data structures by adopting C99 compound literal initializers. This change streamlines the code by replacing explicit memset calls with a more concise and type-safe method for zero-initializing structs and arrays, enhancing overall code quality and maintainability.

Highlights

  • Modernized Initialization: Replaced numerous instances of memset(..., 0, sizeof(...)) with C99 compound literal initializers like (type){0} for structs and arrays across the codebase.
  • Improved Readability and Safety: The use of compound literals makes the intent of zero-initialization clearer and can prevent common memset errors related to incorrect size arguments.
  • Consistency: Standardized the approach to zero-initializing various data structures, including crypto contexts, connection IDs, client structures, and packet headers.

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Changelog
  • crypto/gnutls/gnutls.c
    • Replaced memset with static const uint8_t iv[16] = {0}; for IV array initialization.
  • crypto/picotls/picotls.c
    • Updated ngtcp2_crypto_picotls_ctx_init to use compound literal initialization for the entire cptls struct.
  • crypto/shared.c
    • Initialized plaintext arrays directly at declaration with {0}, removing subsequent memset calls.
  • examples/gtlssimpleclient.c
    • Changed client struct initialization from memset to compound literal *c = (struct client){0};.
  • examples/simpleclient.c
    • Changed client struct initialization from memset to compound literal *c = (struct client){0};.
  • lib/ngtcp2_cid.c
    • Updated ngtcp2_cid_zero to use compound literal initialization for ngtcp2_cid.
  • lib/ngtcp2_conn.c
    • Replaced memset calls with compound literal initialization for ngtcp2_crypto_cipher_ctx structs in various key installation and discard functions.
  • tests/ngtcp2_conn_test.c
    • Replaced memset calls with compound literal initialization for my_user_data and ngtcp2_pkt_hd structs in test cases.
  • tests/ngtcp2_pkt_test.c
    • Replaced memset calls with compound literal initialization for ngtcp2_stream, ngtcp2_connection_close, ngtcp2_datagram, and ngtcp2_pkt_hd structs in packet encoding/decoding tests.
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Code Review

This pull request refactors the codebase to use C99 designated initializers ({0}) for zero-initializing structs and arrays, replacing memset. This is a great improvement for code readability and can offer performance benefits. The changes are consistently applied and correct across most of the files.

I've pointed out one area of concern in crypto/gnutls/gnutls.c where a const qualifier is cast away. This could lead to undefined behavior, and I've suggested a safer alternative that still achieves the goal of removing memset.

Overall, this is a solid refactoring effort.

Note: Security Review did not run due to the size of the PR.

crypto/gnutls/gnutls.c
Comment on lines +407 to +410
static const uint8_t iv[16] = {0};
uint8_t buf[16];

gnutls_cipher_set_iv(hd, iv, sizeof(iv));
gnutls_cipher_set_iv(hd, (uint8_t *)iv, sizeof(iv));
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high

Using static const is a good optimization, but casting away const for gnutls_cipher_set_iv is risky, as it could lead to undefined behavior if the function modifies the buffer. A safer approach which still avoids memset is to use a stack-allocated array with an initializer. This ensures that a fresh zeroed buffer is used for each call without the risks of modifying a const object.

    uint8_t iv[16] = {0};
    uint8_t buf[16];

    gnutls_cipher_set_iv(hd, iv, sizeof(iv));

@tatsuhiro-t tatsuhiro-t merged commit 9ac6f9b into main Mar 3, 2026
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@tatsuhiro-t tatsuhiro-t deleted the avoid-memset branch March 3, 2026 08:56
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