bazelbuild/bazel · error

Failed to make absolute path for %s: %s\n

Error message

Failed to make absolute path for %s: %s\n

What it means

launcher_maker is the tool that stamps Windows launchers: it converts each argv path to an absolute Windows path with blaze_util::AsAbsoluteWindowsPath; if that conversion fails (error text explains why, e.g. the path has no valid drive/root or is not representable) it prints this message and exits 1, failing the build action.

Source

Thrown at src/tools/launcher/launcher_maker.cc:47

//  It takes exactly 3 arguments:
//    1) The path to the actual launcher executable
//    2) The multi-line .params file containing the launcher info data
//    3) The path of the output executable
//
//  The program copies the launcher executable as is to the output, and then
//  appends each line of the launch info as a null-terminated string. At the
//  end, the size of the launch data written is appended as a long value (8
//  bytes).

#ifdef _WIN32

#define STRING_TYPE std::wstring
#define STRING_FORMAT "%ls"
std::wstring convert_path(char* path) {
  std::string error;
  std::wstring wpath;
  if (!blaze_util::AsAbsoluteWindowsPath(path, &wpath, &error)) {
    fprintf(stderr, "Failed to make absolute path for %s: %s\n", path,
            error.c_str());
    exit(1);
  }
  return wpath;
}

#else  // _WIN32

#define STRING_TYPE std::string
#define STRING_FORMAT "%s"
std::string convert_path(char* path) { return path; }

#endif  // _WIN32

int main(int argc, char** argv) {
  if (argc < 4) {
    fprintf(stderr, "Expected 3 arguments, got %d\n", argc);
    return 1;

View on GitHub (pinned to e6e199d060)

Solutions

1. Read the '%s' error detail after the colon — it names the exact reason AsAbsoluteWindowsPath refused.
2. Pass fully-qualified Windows paths (C:\...) rather than MSYS-style or bare relative ones.
3. If a rule generates the path, fix the rule to use ctx.expand_make_variables / dep-file rooted absolute paths.
4. Verify the current directory still exists before invoking the tool.

Example fix

# before: launcher_maker.exe launcher.exe info.txt out.exe   (relative args from odd cwd)
# after:
launcher_maker.exe C:\ws\launcher.exe C:\ws\info.txt C:\ws\out.exe

// pre-check the path form before invoking launcher_maker on Windows
bool IsAbsoluteWindowsPath(const std::wstring &p) {
  return p.size() >= 3 && iswalpha(p[0]) && p[1] == L':' && (p[2] == L'\\' || p[2] == L'/');
}

When it happens

Trigger: Passing a launcher, launch-info, or output path that AsAbsoluteWindowsPath rejects: relative paths that cannot be resolved, UNC or device paths in unexpected forms, or invalid drive letters; typically only when launcher_maker is invoked manually or by a rule generating odd paths.

Common situations: Custom rules producing workspace-relative or MSYS-style (/c/foo) paths for Windows launcher actions; running launcher_maker.exe by hand from a shell whose cwd is a deleted directory.

Related errors

• Expected 3 arguments, got %d\n
• Failed to open " STRING_FORMAT ": %s\n
• Failed to create " STRING_FORMAT ": %s\n
• '" + input + "' is not a boolean
• '" + input + "' is not an int

AI-assisted analysis of bazelbuild/bazel@e6e199d060 (2026-08-14). Data as JSON: /api/errors/370eac4ba3a55086. Report an issue: GitHub.