[PATCH] frontend: guard setlocale() consistently with its include

Hello,

Building the 4.0 release on macOS (Apple silicon, Apple clang 21)
stops in the frontend:

  frontend/parse.c:1623:5: error: use of undeclared identifier 'setlocale'
  frontend/parse.c:1623:15: error: use of undeclared identifier 'LC_CTYPE'

This configuration has HAVE_LANGINFO_H but not HAVE_ICONV. parse.c
includes <locale.h> only when both are defined, while the setlocale()
call checks HAVE_LANGINFO_H alone, so the call compiles without the
declaration of setlocale() or the definition of LC_CTYPE. In this
build the shipped configure script (generated by Autoconf 2.73)
selected -std=gnu23, and Apple clang 21 reports both missing names as
errors.

The patch below gives the call the same guard as the existing
include, which is the smallest change; including <locale.h> more
broadly would be another possible fix if you would rather keep the
call active in iconv-less builds. Verified locally: the pristine 4.0
tree fails as above, and the patched tree builds and encodes.

The patch is against current trunk (r6586) and also applies to the
4.0 release (offset -33 lines).

Maya

-- >8 --
From: Maya <[email protected]>
Date: Thu, 16 Jul 2026 15:28:13 -0400
Subject: [PATCH] frontend: guard setlocale() consistently with its include

parse.c includes <locale.h> only when both HAVE_ICONV and
HAVE_LANGINFO_H are defined, but the setlocale(LC_CTYPE, "") call at
the top of parse_args() checks HAVE_LANGINFO_H alone. In a
configuration that has langinfo.h but not iconv, the call therefore
compiles without the declaration of setlocale() or the definition of
LC_CTYPE. Seen building the 4.0 release on macOS: the shipped
configure (generated by Autoconf 2.73) selected -std=gnu23 in this
build, and Apple clang 21 reports both missing names as errors, so
the frontend fails to build.

Give the call the same guard as the existing include.
---
 frontend/parse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/frontend/parse.c b/frontend/parse.c
index 94c7e95..85128b2 100644
--- a/frontend/parse.c
+++ b/frontend/parse.c
@@ -1652,7 +1652,7 @@ parse_args_(lame_global_flags * gfp, int argc,
char **argv,
     enum TextEncoding id3_tenc = TENC_LATIN1;
 #endif

-#ifdef HAVE_LANGINFO_H
+#if defined(HAVE_ICONV) && defined(HAVE_LANGINFO_H)
     setlocale(LC_CTYPE, "");
 #endif
     inPath[0] = '\0';