Config check fail despite prerequisites being fulfilled

[Taiki-San]

Description

• Type: Bug
• Priority: Minor

Disabling all elliptic curves besides MBEDTLS_ECP_DP_CURVE25519_ENABLED doesn't fulfill the requirements of MBEDTLS_ECP_C, despite the description mentioning only MBEDTLS_BIGNUM_C (enabled) and at least one MBEDTLS_ECP_DP_XXX_ENABLED.

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Bug

mbed TLS build:
Version: 1bf6123

Expected behavior
mbedTLS compiles with all but one curve being enabled, as shown below.

// #define MBEDTLS_ECP_DP_SECP224R1_ENABLED
// #define MBEDTLS_ECP_DP_SECP256R1_ENABLED
// #define MBEDTLS_ECP_DP_SECP384R1_ENABLED
// #define MBEDTLS_ECP_DP_SECP521R1_ENABLED
// #define MBEDTLS_ECP_DP_SECP192K1_ENABLED
// #define MBEDTLS_ECP_DP_SECP224K1_ENABLED
// #define MBEDTLS_ECP_DP_SECP256K1_ENABLED
// #define MBEDTLS_ECP_DP_BP256R1_ENABLED
// #define MBEDTLS_ECP_DP_BP384R1_ENABLED
// #define MBEDTLS_ECP_DP_BP512R1_ENABLED
#define MBEDTLS_ECP_DP_CURVE25519_ENABLED

Actual behavior

Compilation fail with error message
../include/mbedtls/check_config.h:122:2: error: #error "MBEDTLS_ECP_C defined, but not all prerequisites"

Steps to reproduce

Disable most curves, while letting MBEDTLS_ECP_DP_CURVE25519_ENABLED defined.
check_config.h will then check the requirements of MBEDTLS_ECP_C which are missing this specific curve, despite the documentation implying otherwise

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Question

Is this behavior intentional?
I can prepare a PR to add MBEDTLS_ECP_DP_CURVE25519_ENABLED to the check if that's simply an oversight.

[Taiki-San]

Duplicate of #941