bench: fail early if user inputs invalid value for SECP256K1_BENCH_ITERS #1796

pull kevkevinpal wants to merge 1 commits into bitcoin-core:master from kevkevinpal:failEarlyOnInvalidIters changing 4 files +23 −4

kevkevinpal commented at 6:15 PM on January 8, 2026: contributor

Description

Motivated by #1793 (comment)

In this change, the get_iters function was updated to print an error message and then return 0.

In the functions that use get_iters they print the help text and then EXIT_FAILURE

Before

secp256k1 $ SECP256K1_BENCH_ITERS=abc ./build/bin/bench

Benchmark                     ,    Min(us)    ,    Avg(us)    ,    Max(us)

Floating point exception (core dumped)

After

secp256k1 $ SECP256K1_BENCH_ITERS=abc ./build/bin/bench

Invalid value for SECP256K1_BENCH_ITERS must be a positive integer: abc

Benchmarks the following algorithms:
    - ECDSA signing/verification
    - ECDH key exchange (optional module)
    - Schnorr signatures (optional module)
    - ElligatorSwift (optional module)

The default number of iterations for each benchmark is 20000. This can be
customized using the SECP256K1_BENCH_ITERS environment variable.

Usage: ./bench [args]
By default, all benchmarks will be run.
args:
    help              : display this help and exit
    ecdsa             : all ECDSA algorithms--sign, verify, recovery (if enabled)
    ecdsa_sign        : ECDSA siging algorithm
    ecdsa_verify      : ECDSA verification algorithm
    ec                : all EC public key algorithms (keygen)
    ec_keygen         : EC public key generation
    ecdh              : ECDH key exchange algorithm
    schnorrsig        : all Schnorr signature algorithms (sign, verify)
    schnorrsig_sign   : Schnorr sigining algorithm
    schnorrsig_verify : Schnorr verification algorithm
    ellswift          : all ElligatorSwift benchmarks (encode, decode, keygen, ecdh)
    ellswift_encode   : ElligatorSwift encoding
    ellswift_decode   : ElligatorSwift decoding
    ellswift_keygen   : ElligatorSwift key generation
    ellswift_ecdh     : ECDH on ElligatorSwift keys

kevkevinpal force-pushed on Jan 8, 2026
kevkevinpal force-pushed on Jan 8, 2026
real-or-random added the label tweak/refactor on Jan 8, 2026

in src/bench.h:156 in 331bb48bed

 149 | @@ -150,7 +150,13 @@ static int have_invalid_args(int argc, char** argv, char** valid_args, size_t n)
 150 |  static int get_iters(int default_iters) {
 151 |      char* env = getenv("SECP256K1_BENCH_ITERS");
 152 |      if (env) {
 153 | -        return strtol(env, NULL, 0);
 154 | +        char* endptr;
 155 | +        long int iters = strtol(env, &endptr, 0);
 156 | +        if (*endptr != '\0' || iters == 0) {
 157 | +            printf("Invalid value for SECP256K1_BENCH_ITERS must be a positive integer: %s\n\n", env);

real-or-random commented at 8:30 AM on January 9, 2026:

            printf("Error: Value of SECP256K1_BENCH_ITERS is not a positive integer: %s\n\n", env);

nit:
I think the wording "invalid value .... must be a positive integer" is a bit confusing.

kevkevinpal commented at 2:20 PM on January 9, 2026:

Thanks for the review l, I took your suggestion and fixed it in a02ea3566c28e1e919ca8e037c42dad4ec223138

in src/bench.h:155 in 331bb48bed

 149 | @@ -150,7 +150,13 @@ static int have_invalid_args(int argc, char** argv, char** valid_args, size_t n)
 150 |  static int get_iters(int default_iters) {
 151 |      char* env = getenv("SECP256K1_BENCH_ITERS");
 152 |      if (env) {
 153 | -        return strtol(env, NULL, 0);
 154 | +        char* endptr;
 155 | +        long int iters = strtol(env, &endptr, 0);
 156 | +        if (*endptr != '\0' || iters == 0) {

real-or-random commented at 8:32 AM on January 9, 2026:

        if (*endptr != '\0' || iters <= 0) {

kevkevinpal commented at 2:19 PM on January 9, 2026:

Thanks for the review! I fixed this in a02ea3566c28e1e919ca8e037c42dad4ec223138

hebasto commented at 4:55 PM on January 9, 2026:

Right. Otherwise, negative values are accepted:

$ SECP256K1_BENCH_ITERS=-1 ./build/bin/bench
Benchmark                     ,    Min(us)    ,    Avg(us)    ,    Max(us)    

ecdsa_verify                  ,     0.0       ,    -0.300     ,    -1.00   
ecdsa_sign                    ,     0.0       ,    -0.100     ,    -1.00   
ec_keygen                     ,     0.0       ,     0.0       ,     0.0    
ecdh                          ,     0.0       ,     0.0       ,     0.0    
ecdsa_recover                 ,     0.0       ,    -0.100     ,    -1.00   
schnorrsig_sign               ,     0.0       ,     0.0       ,     0.0    
schnorrsig_verify             ,     0.0       ,     0.0       ,     0.0    
ellswift_encode               ,     0.0       ,    -0.200     ,    -1.00   
ellswift_decode               ,     0.0       ,     0.0       ,     0.0    
ellswift_keygen               ,     0.0       ,    -0.100     ,    -1.00   
ellswift_ecdh                 ,     0.0       ,    -0.100     ,    -1.00

real-or-random commented at 8:32 AM on January 9, 2026: contributor

ACK mod nits
kevkevinpal force-pushed on Jan 9, 2026
hebasto approved
hebasto commented at 4:56 PM on January 9, 2026: member

ACK a02ea3566c28e1e919ca8e037c42dad4ec223138, I have reviewed the code and it looks OK. Tested on Ubuntu 25.10.
real-or-random commented at 1:34 PM on January 13, 2026: contributor

Needs rebase (on your own stuff) :)
kevkevinpal force-pushed on Jan 23, 2026
kevkevinpal commented at 1:05 PM on January 23, 2026: contributor

Needs rebase (on your own stuff) :)

Sorry was traveling for a bit, rebased to c09215f

bench: fail early if user inputs invalid value for SECP256K1_BENCH_ITERS

In this change the get_iters function was updated to print an error
message and then return 0. In the functions that use get_iters they
print the help text and then EXIT_FAILURE

c09215f7af

kevkevinpal force-pushed on Jan 23, 2026
hebasto approved
hebasto commented at 1:20 PM on January 23, 2026: member

re-ACK c09215f7af9db3e34427ff9a5633e7978acabca1.
real-or-random approved
real-or-random commented at 1:29 PM on January 23, 2026: contributor

utACK c09215f7af9db3e34427ff9a5633e7978acabca1
real-or-random merged this on Jan 23, 2026
real-or-random closed this on Jan 23, 2026

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#1793 doc/bench: added help text for SECP256K1_BENCH_ITERS env var for bench_ecmult