nodejs/node · error

Unable to create map file: %s.\n

Error message

Unable to create map file: %s.\n

What it means

pkgdata cannot open the generated .map (linker map) file for writing. The filename is built from o->shortName + MAP_FILE_EXT and opened with T_FileStream_open(...,"w"). A nullptr return means the filesystem refused the create — typically a permission denial, a read-only build directory, a full disk, or an invalid shortName producing an illegal filename. The tool returns nullptr from the calling function, aborting map-file generation for that library mode.

Source

Thrown at deps/icu-small/source/tools/pkgdata/pkgdata.cpp:1988

                }
            }

            tmpbuffer[index++] = flag[i];

            if (flag[i] == 0) {
                break;
            }
        }

        uprv_memset(flag, 0, length);
        uprv_strcpy(flag, tmpbuffer);

        uprv_strcpy(mapFile, o->shortName);
        uprv_strcat(mapFile, MAP_FILE_EXT);

        f = T_FileStream_open(mapFile, "w");
        if (f == nullptr) {
            fprintf(stderr,"Unable to create map file: %s.\n", mapFile);
            return nullptr;
        } else {
            snprintf(tmpbuffer, sizeof(tmpbuffer), "%s%s ", o->entryName, UDATA_CMN_INTERMEDIATE_SUFFIX);
    
            T_FileStream_writeLine(f, tmpbuffer);
    
            T_FileStream_close(f);
        }
    }
#elif U_PLATFORM == U_PF_CYGWIN || U_PLATFORM == U_PF_MINGW
    /* Cygwin needs to change flag options. */
    char *flag = nullptr;
    int32_t length = 0;

    flag = pkgDataFlags[GENLIB];
    length = static_cast<int32_t>(uprv_strlen(pkgDataFlags[GENLIB]));

    int32_t position = length - 1;

View on GitHub (pinned to 1b2de5e052)

Solutions

1. Verify the working directory is writable: touch the build dir as the build user.
2. Run the build with adequate disk space (df -h .).
3. Check that -O/--shortName (or the ICU_DATA short name) contains no path separators or illegal filename characters.
4. Ensure no directory named <shortName>.map already exists in the output location.

Example fix

// before: build into read-only tree
make install  # runs as user without write perms

// after: write into a user-writable staging dir
mkdir -p /tmp/icu-stage && make DESTDIR=/tmp/icu-stage install

// Validate the output directory is writable and the map filename is legal before invoking pkgdata.
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>

bool canWriteMapFile(const char *outdir, const char *shortName) {
    if (access(outdir, W_OK | X_OK) != 0) return false;     // need write+search on dir
    struct stat st;
    char path[PATH_MAX];
    snprintf(path, sizeof(path), "%s/%s.map", outdir, shortName);
    if (stat(path, &st) == 0 && S_ISDIR(st.st_mode)) return false; // name collides with a dir
    for (const char *p = shortName; *p; ++p)
        if (*p == '/' || *p == '\\') return false;          // shortName must be a bare name
    return true;
}

When it happens

Trigger: Reached only in the branch that writes a map file (the non-Cygwin/Mingw path guarded by the #elif above). T_FileStream_open(mapFile,"w") returns nullptr. Triggers when the CWD or output dir is not writable, when o->shortName contains path separators/illegal chars, or when MAP_FILE_EXT resolves to a name that already exists as a directory.

Common situations: Building ICU data into a directory the build user cannot write (e.g. make install running as non-root into /usr), NFS-mounted read-only source trees, out-of-disk conditions during a parallel build, or a shortName set from a package name containing a slash.

Related errors

• T_FileStream_open failed to open %s for writing\n
• Error creating symbolic links of the data library file.
• Error creating installation directory: %s\n
• U_FILE_ACCESS_ERROR
• T_FileStream_remove failed to delete %s\n

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/572b5c06bca79ee9. Report an issue: GitHub.