dotnet/runtime · error · Error

Locale info for locale=${localeName} exceeds length of ${dst

Error message

Locale info for locale=${localeName} exceeds length of ${dstMaxLength}.

What it means

The resolved locale display string (language + region joined by "##") is checked against dstMaxLength — the size of the destination buffer the native caller allocated. If localized names are verbose enough to exceed it, the function refuses to write a truncated result and throws. The catch marshals the message to .NET with dstLength=-1.

Source

Thrown at src/native/libs/System.Native.Browser/native/globalization-locale.ts:66

                        return 0 as any;
                    }
                    throw error;
                }
            } else {
                throw error;
            }
        }
        const localeInfo = {
            LanguageName: languageName,
            RegionName: regionName,
        };
        const result = Object.values(localeInfo).join(OUTER_SEPARATOR);

        if (!result)
            throw new Error(`Locale info for locale=${localeName} is null or empty.`);

        if (result.length > dstMaxLength)
            throw new Error(`Locale info for locale=${localeName} exceeds length of ${dstMaxLength}.`);

        _ems_.dotnetBrowserUtilsExports.stringToUTF16(dst, dst + 2 * result.length, result);
        _ems_.dotnetApi.setHeapI32(dstLength, result.length);
        return 0 as any;
    } catch (ex: any) {
        _ems_.dotnetApi.setHeapI32(dstLength, -1);
        return _ems_.dotnetBrowserUtilsExports.stringToUTF16Ptr(ex.toString());
    }

    function normalizeLocale(locale: string | null) {
        if (!locale)
            return undefined;
        try {
            locale = locale.toLocaleLowerCase().replace("_", "-");
            if (locale.startsWith("zh-")) {
                // browser does not recognize "zh-chs" and "zh-cht" as equivalents of "zh-Hans" "zh-Hant", we are helping, otherwise
                // it would throw on getCanonicalLocales with "RangeError: Incorrect locale information provided"
                locale = locale.replace("-chs", "-Hans").replace("-cht", "-Hant");

View on GitHub (pinned to 290d5ab72c)

Solutions

Update to a newer dotnet runtime, which allocates a larger destination buffer for locale info.
If invoking the native API directly, allocate a destination buffer at least as large as the longest expected display-name pair.
Catch the error in .NET and retry with the invariant (English) culture, which yields shorter names.

Defensive patterns

Strategy: fallback

Try / catch

try { localeInfo = GetLocaleInfo(locale, culture, buffer, bufferLen); }
catch { localeInfo = GetLocaleInfo(locale, "en" /* invariant-ish */, buffer, bufferLen); }

Prevention

Keep the dotnet runtime up to date; locale-info buffer sizes have increased in newer versions.
Provide an invariant (English) culture fallback, which yields shorter display names.
If calling the native API directly, size the destination buffer generously.

When it happens

Trigger: A locale whose resolved display names in the target culture produce a combined string longer than the dstMaxLength buffer the runtime passed in.

Common situations: Cultures/scripts with long translated display names exceeding the native buffer; running against an older dotnet runtime version that allocates a smaller buffer than the current one.

Related errors

AI-assisted analysis of dotnet/runtime@290d5ab72c (2026-08-06). Data as JSON: /api/errors/47ff0262c69377d5. Report an issue: GitHub.