README.rst: begin documenting quirks

diff --git a/README.rst b/README.rst
index aa134dbe5b3f8cc3e6466faa590a388cc3ba8595..cfd1df8b691164bf8081aa381e83d839c35dfa52 100644 (file)
--- a/README.rst
+++ b/README.rst
@@ -11,3 +11,21 @@ Implementations:
 * `musl libc <https://musl.libc.org/>`_
 * `GNU libc <https://www.gnu.org/software/libc/>`_
 * `GNU libiconv <https://www.gnu.org/software/libiconv/>`_
+
+Quirks by implementation
+========================
+
+Not technically illegal, but perhaps unexpected.
+
+musl
+----
+
+* iconv_open() supports neither ``//IGNORE`` nor ``//TRANSLIT`` as an
+  indicator suffices.
+
+glibc
+-----
+
+* iconv_open() accepts any indicator suffix, such as ``//INVALID``.
+* iconv() returns EILSEQ when it ignores invalid input.
+