Unless otherwise configured, the client libraries use Application Default Credentials to authenticate with Google Cloud Services. While this works for most applications, in some cases you may need to override this default. You can do so by providing the UnifiedCredentialsOption The following example shows how to explicitly load a service account key file:
[](std::string const& keyfile) {
auto is = std::ifstream(keyfile);
is.exceptions(std::ios::badbit); // Minimal error handling in examples
auto contents = std::string(std::istreambuf_iterator<char>(is.rdbuf()), {});
auto options =
google::cloud::Options{}.set<google::cloud::UnifiedCredentialsOption>(
google::cloud::MakeServiceAccountCredentials(contents));
return google::cloud::functions_v1::CloudFunctionsServiceClient(
google::cloud::functions_v1::MakeCloudFunctionsServiceConnection(
options));
}
Follow these links to find examples for other *Client classes:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThe webpage provides documentation for various versions of C++ client libraries, ranging from version 2.11.0 to the latest release candidate 2.37.0-rc, with version 2.30.0 being the currently viewed version.\u003c/p\u003e\n"],["\u003cp\u003eThe content describes how to override the default Application Default Credentials used for authenticating with Google Cloud Services by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eAn example is given showing how to load a service account key file explicitly using \u003ccode\u003egoogle::cloud::MakeServiceAccountCredentials\u003c/code\u003e and \u003ccode\u003egoogle::cloud::Options\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eExamples for other client classes, such as \u003ccode\u003efunctions_v1::CloudFunctionsServiceClient\u003c/code\u003e and \u003ccode\u003efunctions_v2::FunctionServiceClient\u003c/code\u003e, can be found via provided links.\u003c/p\u003e\n"],["\u003cp\u003eThe document refers users to the best practices guide for managing service account keys and the authentication components documentation for more details.\u003c/p\u003e\n"]]],[],null,[]]
