doc: describe dropping unused tables from static builds #1973

pull fametrano wants to merge 1 commits into bitcoin-core:master from fametrano:docs-gc-sections changing 1 files +12 −0

fametrano commented at 8:21 PM on October 21, 2026: contributor

doc: describe dropping unused tables from static builds

Adds a short README section: compile with -ffunction-sections -fdata-sections and link with -Wl,--gc-sections, so a static build drops the precomputed tables and code a program never calls. A verification-only program should use secp256k1_context_static, because a context from secp256k1_context_create keeps the signing table linked in.

Addresses the last open item of #1065 (the other items are checked). real-or-random agreed to a docs PR in the thread.

Size of text in bytes, static library built with the default modules and CFLAGS="-g -O2", plus the section flags in the last column:

program	no flags	sections + gc
signing only (ECDSA + Schnorr)	1340145	131364
verifying only, `context_static`	1340313	1128701
verifying only, `context_create`	1340281	1234429

Measured with size and nm on the linked binaries (Debian trixie, aarch64, GCC 14.2, GNU ld 2.44); Autotools and CMake give identical sizes.

doc: describe dropping unused tables from static builds

Compiling with -ffunction-sections -fdata-sections and linking with
-Wl,--gc-sections lets the linker drop the precomputed tables and code
that a program never calls. Document it in the README, with the sizes
measured for a signing-only and a verification-only program.

Addresses the last open item of #1065.

Assisted-by: Claude Opus 5.5

2e5529f275

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fametrano

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#1065 Further changes after making tables static