How does bazel use WITH_CUSTOM_PREFIX flag？

[luliyucoordinate]

I want to change log prefix format. And I see the sentence "That feature must be enabled at compile time by the WITH_CUSTOM_PREFIX flag." in the document. But how do I use it in bazel?

[sergiud]

WITH_CUSTOM_PREFIX is a CMake option. In Bazel, you need to define GLOG_CUSTOM_PREFIX_SUPPORT.

[luliyucoordinate]

When I defined GLOG_CUSTOM_PREFIX_SUPPORT at the beginning

#define GLOG_CUSTOM_PREFIX_SUPPORT
#include <iostream>
#include <iomanip>
#include <glog/logging.h>

using std::setw;
using std::setfill;


/* This function writes a prefix that matches glog's default format.
 * (The third parameter can be used to receive user-supplied data, and is
 * NULL by default.)
 */
void CustomPrefix(std::ostream &s, const LogMessageInfo &l, void*) {
   s << l.severity[0]
   << setw(4) << 1900 + l.time.year()
   << setw(2) << 1 + l.time.month()
   << setw(2) << l.time.day()
   << ' '
   << setw(2) << l.time.hour() << ':'
   << setw(2) << l.time.min()  << ':'
   << setw(2) << l.time.sec() << "."
   << setw(6) << l.time.usec()
   << ' '
   << setfill(' ') << setw(5)
   << l.thread_id << setfill('0')
   << ' '
   << l.filename << ':' << l.line_number << "]";
}

int main(int argc, char* argv[]) {
    // FLAGS_log_dir  = "./log";
    google::InitGoogleLogging(argv[0], &CustomPrefix);
    FLAGS_logtostderr = 1;
    int num_cookies = 10;
    LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";

    for (int i = 0; i < 30; i++) {
        LOG_EVERY_N(INFO, 10) << "Got the " << google::COUNTER << "th cookie";
    }

    DLOG(INFO) << "Found cookies";
    // CHECK_EQ(1, 2) << ": The world must be ending!";

    FLAGS_v = 2;
    VLOG(1) << "I’m printed when you run the program with --v=1 or higher";
    VLOG(2) << "I’m printed when you run the program with --v=2 or higher";

    google::ShutdownGoogleLogging();
}

and l get error

bazel-out/k8-fastbuild/bin/_objs/main/main.pic.o:main.cc:function main: error: undefined reference to 'google::InitGoogleLogging(char const*, void (*)(std::ostream&, LogMessageInfo const&, void*), void*)'
collect2: error: ld returned 1 exit status
Target //:main failed to build

[sergiud]

/cc @drigz

[drigz]

@luliyucoordinate The current Bazel integration doesn't seem to support it. You could try running bazel build --copt=-DGLOG_CUSTOM_PREFIX_SUPPORT .... If that helps, you could try adding it to common_copts in glog.bzl and sending a PR.

[luliyucoordinate]

@drigz it works, then l sending a PR bazel: add GLOG_CUSTOM_PREFIX_SUPPORT