Tolerate duplicate iconv aliases on macOS

[pnavais]

On macOS, iconv -l lists some charset aliases under more than one group. In particular, WINDOWS-874 appears with both CP1162 and CP874. When tables.py turns that listing into iconvdecl.h, module_iconv then tries to declare the same alias for two different charsets and aborts initialization with a contradiction error. That makes the check phase fail on aarch64-darwin (and likely x86_64-darwin as well).

This change:

1. In tables.py, when digesting iconv -l, keep only the first occurrence of each alias name.
2. In module_iconv, if an alias is already bound to a different charset, keep the existing binding instead of failing.

Verified on aarch64-darwin with recode 3.7.16: 488 good tests.

[pnavais]

For reference, the macOS job in the existing CI already fails on master with this bug, and it affects both architectures:

• Current master workflow plus an Intel macOS job: macos-latest (arm64) and macos-15-intel (x86_64) both fail with Charset WINDOWS-874 already exists and is not CP874.
• The same workflow with this PR merged: all jobs pass on macOS arm64, macOS x86_64, Ubuntu, and both Windows setups.

I've opened #82 with those workflow changes, adding Intel macOS and fixing the Homebrew paths and the ASAN preload. It depends on this PR, so the two can be reviewed and merged together.

[rrthomas]

Thanks for this!

[dwt]

As this is triggering a build failure for fortune in nixpkgs - can you guys perhaps give us a hint when this will be released?

[pnavais]

Hi @dwt !

Agreed this needs a release for packagers. The fix is already on master (#81, slightly simplified by @rrthomas on merge); #82 also landed so macOS CI (arm64 + Intel) is green again. A new release is up to @rrthomas (likely 3.7.17). Once that tag/tarball is out, nixpkgs can bump recode from 3.7.16.

Until then, from my side, I'm currently applying a small overlay to have fortune-mod + recode build on nix-darwin (It's basically the same change included in this PR)

Sharing here in case you find it useful :

overlays/recode.nix

# macOS libiconv lists some aliases (e.g. WINDOWS-874) under more than one
# charset group. recode 3.7.16 treats that as a fatal init error and fails
# its check phase on aarch64-darwin. Keep the first binding instead.
final: prev: {
  recode = prev.recode.overrideAttrs (old: {
    patches = (old.patches or []) ++ [
      ./recode-darwin-iconv-aliases.patch
    ];
  });
}

overlays/recode-darwin-iconv-aliases.patch

diff --git a/src/iconv.c b/src/iconv.c
index a44fd8c..c96fed0 100644
--- a/src/iconv.c
+++ b/src/iconv.c
@@ -272,11 +272,18 @@ module_iconv (RECODE_OUTER outer)
 	  RECODE_ALIAS alias
 	    = recode_find_alias (outer, *cursor, ALIAS_FIND_AS_CHARSET);
 
-	  /* If there is a charset contradiction, call recode_declare_alias
-	     nevertheless, as the error processing will occur there.  */
-	  if (!alias || alias->symbol->name != charset_name)
-	    if (!recode_declare_alias (outer, *cursor, charset_name))
-	      return false;
+	  if (!alias)
+	    {
+	      if (!recode_declare_alias (outer, *cursor, charset_name))
+		return false;
+	    }
+	  else if (alias->symbol->name != charset_name)
+	    {
+	      /* Some iconv implementations (notably macOS libiconv) list the
+		 same alias under more than one charset group — e.g.
+		 WINDOWS-874 appears with both CP1162 and CP874.  Keep the
+		 first binding instead of aborting initialization.  */
+	    }
 	}
     }
 
diff --git a/tables.py b/tables.py
index 1d7bc9a..aecaade 100755
--- a/tables.py
+++ b/tables.py
@@ -468,6 +468,7 @@ class Iconv(Options):
         libc = None
         import os
         names = []
+        seen = set()
         for line in os.popen('iconv -l'):
             if libc is None:
                 libc = len(line.split('/')) == 3
@@ -484,7 +485,19 @@ class Iconv(Options):
                     if alias in canonical:
                         alias = canonical[alias]
                     aliases.append(alias)
-                self.data.append((aliases[0], aliases[1:]))
+                # Prefer the first charset group for each alias name.  Some
+                # iconv implementations (macOS libiconv) repeat names across
+                # groups — e.g. WINDOWS-874 under both CP1162 and CP874 —
+                # which would otherwise make module_iconv abort.
+                filtered = []
+                for alias in aliases:
+                    key = alias.upper()
+                    if key in seen:
+                        continue
+                    seen.add(key)
+                    filtered.append(alias)
+                if filtered:
+                    self.data.append((filtered[0], filtered[1:]))
 
     def complete(self, french):
         def write_charset(format, charset):

[rrthomas]

Releasing 3.7.17 now.

[pnavais]

Thanks a lot Reuben !

[pnavais]

Bot already created the PR on nixpkgs : NixOS/nixpkgs#571390

Let's see if this gets merged soon.