configure.ac refuses --enable-module-frost, --enable-module-chilldkg and
--enable-module-iceberg outright unless --enable-experimental is also
given. The CMake build had no equivalent, so
-DSECP256K1_ENABLE_MODULE_ICEBERG=ON produced a library with no warning
banner and no acknowledgement that anything experimental was requested.
Of the three, iceberg is the one this matters most for: doc/iceberg.md
tells the reader not to put money behind it, and the CMake path let a
build acquire it without the reader ever passing a flag that says so.
Add the three checks to the existing NOT SECP256K1_EXPERIMENTAL block,
next to the ARM32 assembly check and worded the same way. The options are
declared well above it, so the values are set by the time the block runs.
Verified both directions: the configure fails with "Iceberg module is
experimental. Use -DSECP256K1_EXPERIMENTAL=ON to allow." without the
flag, and succeeds with it.
This deliberately leaves the other zkp experimental modules alone. They
are ON by default in CMake and gating them would change every existing
CMake build; the three added here are OFF by default, so nobody is
relying on the ungated path.
While here, correct doc/iceberg.md, which claimed the module "builds by
default here". SECP_SET_DEFAULT(enable_module_iceberg, no, yes) makes it
off by default and on in dev mode, which is now what the paragraph says,
along with the experimental requirement it did not previously mention.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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