What causes "genccode: filename too long " in nodejs/node?

Shorten the destination directory path (-d) to reduce total length.

U_ILLEGAL_ARGUMENT_ERROR

U_ILLEGAL_ARGUMENT_ERROR

Error message

genccode: filename too long

What it means

Thrown by genccode's writeAssemblyCode when the computed output filename length is greater than or equal to the caller-provided outFilePathCapacity. This is a buffer-safety guard: the resolved path would not fit in the caller's outFilePath buffer, so it aborts before copying.

Source

Thrown at deps/icu-small/source/tools/toolutil/pkg_genc.cpp:369

    getOutFilename(
        filename,
        destdir,
        buffer.chars,
        sizeof(buffer.chars),
        entry,
        sizeof(entry),
        newSuffix,
        optFilename);
    out=T_FileStream_open(buffer.chars, "w");
    if(out==nullptr) {
        fprintf(stderr, "genccode: unable to open output file %s\n", buffer.chars);
        exit(U_FILE_ACCESS_ERROR);
    }

    if (outFilePath != nullptr) {
        if (uprv_strlen(buffer.chars) >= outFilePathCapacity) {
            fprintf(stderr, "genccode: filename too long\n");
            exit(U_ILLEGAL_ARGUMENT_ERROR);
        }
        uprv_strcpy(outFilePath, buffer.chars);
#if defined (WINDOWS_WITH_GNUC) && U_PLATFORM != U_PF_CYGWIN
        /* Need to fix the file separator character when using MinGW. */
        swapFileSepChar(outFilePath, U_FILE_SEP_CHAR, '/');
#endif
    }

    if(optEntryPoint != nullptr) {
        uprv_strcpy(entry, optEntryPoint);
        uprv_strcat(entry, "_dat");
    }

    /* turn dashes or dots in the entry name into underscores */
    length=uprv_strlen(entry);
    for(i=0; i<length; ++i) {
        if(entry[i]=='-' || entry[i]=='.') {

View on GitHub (pinned to 1b2de5e052)

Solutions

Shorten the destination directory path (-d) to reduce total length.
Increase the outFilePath buffer size in the calling code (the build system / Makefile).
Move the build root closer to the filesystem root to trim path depth.
Use relative paths where the build system allows.

Example fix

// before (caller)
char outFilePath[64];
writeAssemblyCode(..., outFilePath, sizeof(outFilePath)); // too short

// after
char outFilePath[PATH_MAX];
writeAssemblyCode(..., outFilePath, sizeof(outFilePath));

Defensive patterns

Strategy: validation

Validate before calling

// Before calling writeAssemblyCode, ensure your outFilePath buffer is large
// enough for any plausible output path.
#include <climits>   // PATH_MAX
#include <cstring>
bool pathBufferAdequate(size_t cap, const char* destdir, const char* name) {
    size_t need = std::strlen(destdir) + std::strlen(name) + 8; // sep + suffix + slop
    return cap > need && cap >= PATH_MAX;
}

Prevention

Allocate outFilePath with at least PATH_MAX bytes in the calling code.
Keep the -d destdir short to minimize total path length.
Validate the computed path length before passing the buffer to genccode.
Prefer relative build paths where the build system supports them.

When it happens

Trigger: When outFilePath != nullptr, the code checks uprv_strlen(buffer.chars) >= outFilePathCapacity before uprv_strcpy. Failure means the path (destdir + name + suffix) is too long for the receiving buffer.

Common situations: Very deep build directory trees; very long ICU data filenames; deeply nested absolute paths on Windows; a caller passing a too-small buffer; symlink-heavy paths that expand.

Related errors

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/2f080364f5902524. Report an issue: GitHub.