Subject: [PATCH v3 2/2] macOS: use iconv from Homebrew if present

From: René Scharfe <[email-masked]>
Date: Tue, 16 Dec 2025 19:53:53 +0100

The library function iconv(3) supplied with macOS versions 15.7.2
(Sequoia) and 26.1 (Tahoe) is unreliable when doing conversions from
ISO-2022-JP to UTF-8 in multiple steps; t3900 reports this breakage:

  not ok 17 - ISO-2022-JP should be shown in UTF-8 now
  not ok 25 - ISO-2022-JP should be shown in UTF-8 now
  not ok 38 - commit --fixup into ISO-2022-JP from UTF-8

As a workaround, use libiconv from Homebrew, if available.  Search it in
its default locations: /opt/homebrew for Apple Silicon and /usr/local
for macOS Intel, with the former taking precedence.  Respect ICONVDIR if
already set by the user, though.

Helped-by: Koji Nakamaru <[email-masked]>
Signed-off-by: René Scharfe <[email-masked]>
---
 Makefile         | 8 ++++++++
 config.mak.uname | 1 +
 2 files changed, 9 insertions(+)

diff --git a/Makefile b/Makefile
index a97e9e4d7d..307dac3c03 100644
--- a/Makefile
+++ b/Makefile
@@ -112,6 +112,9 @@ include shared.mak
 # Define USE_HOMEBREW_MSGFMT to use the msgfmt command installed by
 # Homebrew to compile message catalogs during build, if present.
 #
+# Define USE_HOMEBREW_LIBICONV to link against libiconv installed by
+# Homebrew, if present.
+#
 # Define NO_APPLE_COMMON_CRYPTO if you are building on Darwin/Mac OS X
 # and do not want to use Apple's CommonCrypto library.  This allows you
 # to provide your own OpenSSL library, for example from MacPorts.
@@ -1717,6 +1720,11 @@ ifeq ($(shell test -x $(HOMEBREW_PREFIX)/opt/gettext/msgfmt && echo y),y)
 	MSGFMT = $(HOMEBREW_PREFIX)/opt/gettext/msgfmt
 endif
 endif
+ifdef USE_HOMEBREW_LIBICONV
+ifeq ($(shell test -d $(HOMEBREW_PREFIX)/opt/libiconv && echo y),y)
+	ICONVDIR ?= $(HOMEBREW_PREFIX)/opt/libiconv
+endif
+endif
 endif
 endif
 
diff --git a/config.mak.uname b/config.mak.uname
index 54e3a26649..e2e93e9dc5 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -156,6 +156,7 @@ ifeq ($(uname_S),Darwin)
         endif
 	USE_HOMEBREW_GETTEXT = YesPlease
 	USE_HOMEBREW_MSGFMT = YesPlease
+	USE_HOMEBREW_LIBICONV = YesPlease
 
 	# The builtin FSMonitor on MacOS builds upon Simple-IPC.  Both require
 	# Unix domain sockets and PThreads.
-- 
2.52.0