logwrap: convert to C++, rename function logwrap_fork_execvp().

Call the function now logwrap_fork_execvp() and fix const correctness
issues, so no longer do callers need to const_cast<> their args.

Test: logwrapper still works
Change-Id: Iea34f5cae90a06a37d395bf9a91e01fb38c35fa6
diff --git a/logwrapper/logwrapper.cpp b/logwrapper/logwrapper.cpp
new file mode 100644
index 0000000..7118d12
--- /dev/null
+++ b/logwrapper/logwrapper.cpp
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <cutils/klog.h>
+#include <log/log.h>
+#include <logwrap/logwrap.h>
+
+void fatal(const char* msg) {
+    fprintf(stderr, "%s", msg);
+    ALOG(LOG_ERROR, "logwrapper", "%s", msg);
+    exit(-1);
+}
+
+void usage() {
+    fatal("Usage: logwrapper [-a] [-d] [-k] BINARY [ARGS ...]\n"
+          "\n"
+          "Forks and executes BINARY ARGS, redirecting stdout and stderr to\n"
+          "the Android logging system. Tag is set to BINARY, priority is\n"
+          "always LOG_INFO.\n"
+          "\n"
+          "-a: Causes logwrapper to do abbreviated logging.\n"
+          "    This logs up to the first 4K and last 4K of the command\n"
+          "    being run, and logs the output when the command exits\n"
+          "-d: Causes logwrapper to SIGSEGV when BINARY terminates\n"
+          "    fault address is set to the status of wait()\n"
+          "-k: Causes logwrapper to log to the kernel log instead of\n"
+          "    the Android system log\n");
+}
+
+int main(int argc, char* argv[]) {
+    int seg_fault_on_exit = 0;
+    int log_target = LOG_ALOG;
+    bool abbreviated = false;
+    int ch;
+    int status = 0xAAAA;
+    int rc;
+
+    while ((ch = getopt(argc, argv, "adk")) != -1) {
+        switch (ch) {
+            case 'a':
+                abbreviated = true;
+                break;
+            case 'd':
+                seg_fault_on_exit = 1;
+                break;
+            case 'k':
+                log_target = LOG_KLOG;
+                klog_set_level(6);
+                break;
+            case '?':
+            default:
+                usage();
+        }
+    }
+    argc -= optind;
+    argv += optind;
+
+    if (argc < 1) {
+        usage();
+    }
+
+    rc = logwrap_fork_execvp(argc, &argv[0], &status, true, log_target, abbreviated, nullptr);
+    if (!rc) {
+        if (WIFEXITED(status))
+            rc = WEXITSTATUS(status);
+        else
+            rc = -ECHILD;
+    }
+
+    if (seg_fault_on_exit) {
+        uintptr_t fault_address = (uintptr_t)status;
+        *(int*)fault_address = 0;  // causes SIGSEGV with fault_address = status
+    }
+
+    return rc;
+}