What causes "pathname too long: \"%s\"\n" in nodejs/node?

Shorten or flatten the directory path passed as the 'path' argument to icupkg or Package methods.

U_BUFFER_OVERFLOW_ERROR

U_BUFFER_OVERFLOW_ERROR

Error message

pathname too long: \"%s\"\n

What it means

Thrown by makeFullFilename() when prepending a directory path to a filename and the resulting path (strlen(path) + 1 for the null terminator) would exceed or fill the destination buffer capacity. This is a path-length guard on a fixed-size char array (typically 1024 bytes) used for constructing full file paths during package item I/O.

Source

Thrown at deps/icu-small/source/tools/toolutil/package.cpp:258

        if(*t==U_FILE_SEP_CHAR || *t==U_FILE_ALT_SEP_CHAR) {
            *t=U_TREE_ENTRY_SEP_CHAR;
        }
    }
}
#endif

/*
 * Prepend the path (if any) to the name and run the name through treeToName().
 */
static void
makeFullFilename(const char *path, const char *name,
                 char *filename, int32_t capacity) {
    char *s;

    // prepend the path unless nullptr or empty
    if(path!=nullptr && path[0]!=0) {
        if (static_cast<int32_t>(strlen(path) + 1) >= capacity) {
            fprintf(stderr, "pathname too long: \"%s\"\n", path);
            exit(U_BUFFER_OVERFLOW_ERROR);
        }
        strcpy(filename, path);

        // make sure the path ends with a file separator
        s=strchr(filename, 0);
        if(*(s-1)!=U_FILE_SEP_CHAR && *(s-1)!=U_FILE_ALT_SEP_CHAR) {
            *s++=U_FILE_SEP_CHAR;
        }
    } else {
        s=filename;
    }

    // turn the name into a filename, turn tree separators into file separators
    if (static_cast<int32_t>((s - filename) + strlen(name)) >= capacity) {
        fprintf(stderr, "path/filename too long: \"%s%s\"\n", filename, name);
        exit(U_BUFFER_OVERFLOW_ERROR);
    }

View on GitHub (pinned to 1b2de5e052)

Solutions

Shorten or flatten the directory path passed as the 'path' argument to icupkg or Package methods.
Use a working directory closer to the filesystem root and pass shorter relative paths.
Move the ICU data directory to a shorter absolute path.

Example fix

// before
icupkg -a /very/long/build/sandbox/hash123abc/path/to/output/dir
// after
cd /tmp && icupkg -a ./out

Defensive patterns

Strategy: validation

Validate before calling

// Validate path length before calling icupkg with -a or output paths
#include <cstring>
bool isPathLengthSafe(const char* path, int32_t capacity = 1024) {
    return path == nullptr || (static_cast<int32_t>(strlen(path) + 1) < capacity);
}

Prevention

Keep ICU build and staging directories short and close to the filesystem root.
Avoid deeply nested temporary paths in CI environments.
Use relative paths from a sensible working directory.

When it happens

Trigger: Calling readFile(), writePackage(), or any function that calls makeFullFilename() with a path argument whose strlen(path) + 1 >= capacity (1024 for readFile's local buffer). This occurs when the base directory path alone is too long for the filename buffer.

Common situations: Deeply nested build output directories; ICU data staged under very long temporary paths (e.g. CI build sandboxes with hashed paths); running on systems where the source tree has many directory levels.

Related errors

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/7e43e3367b542288. Report an issue: GitHub.