Merge pull request #4892 from khaneliman/bugfix/stab-004-command-exec-failure

fix(command): return non-zero when child exec fails

include/util/command.hpp

@@ -20,6 +20,8 @@ extern std::list<pid_t> reap;
 
 namespace waybar::util::command {
 
+constexpr int kExecFailureExitCode = 127;
+
 struct res {
   int exit_code;
   std::string out;
@@ -114,7 +116,9 @@ inline FILE* open(const std::string& cmd, int& pid, const std::string& output_na
       setenv("WAYBAR_OUTPUT_NAME", output_name.c_str(), 1);
     }
     execlp("/bin/sh", "sh", "-c", cmd.c_str(), (char*)0);
-    exit(0);
+    const int saved_errno = errno;
+    spdlog::error("execlp(/bin/sh) failed in open: {}", strerror(saved_errno));
+    _exit(kExecFailureExitCode);
   } else {
     ::close(fd[1]);
   }
@@ -162,7 +166,9 @@ inline int32_t forkExec(const std::string& cmd, const std::string& output_name)
       setenv("WAYBAR_OUTPUT_NAME", output_name.c_str(), 1);
     }
     execl("/bin/sh", "sh", "-c", cmd.c_str(), (char*)0);
-    exit(0);
+    const int saved_errno = errno;
+    spdlog::error("execl(/bin/sh) failed in forkExec: {}", strerror(saved_errno));
+    _exit(kExecFailureExitCode);
   } else {
     reap_mtx.lock();
     reap.push_back(pid);

test/utils/command.cpp

@@ -0,0 +1,56 @@
+#if __has_include(<catch2/catch_test_macros.hpp>)
+#include <catch2/catch_test_macros.hpp>
+#else
+#include <catch2/catch.hpp>
+#endif
+
+#include <cerrno>
+#include <list>
+#include <mutex>
+#include <sys/wait.h>
+#include <unistd.h>
+
+std::mutex reap_mtx;
+std::list<pid_t> reap;
+
+extern "C" int waybar_test_execl(const char* path, const char* arg, ...);
+extern "C" int waybar_test_execlp(const char* file, const char* arg, ...);
+
+#define execl waybar_test_execl
+#define execlp waybar_test_execlp
+#include "util/command.hpp"
+#undef execl
+#undef execlp
+
+extern "C" int waybar_test_execl(const char* path, const char* arg, ...) {
+  (void)path;
+  (void)arg;
+  errno = ENOENT;
+  return -1;
+}
+
+extern "C" int waybar_test_execlp(const char* file, const char* arg, ...) {
+  (void)file;
+  (void)arg;
+  errno = ENOENT;
+  return -1;
+}
+
+TEST_CASE("command::execNoRead returns 127 when shell exec fails", "[util][command]") {
+  const auto result = waybar::util::command::execNoRead("echo should-not-run");
+  REQUIRE(result.exit_code == waybar::util::command::kExecFailureExitCode);
+  REQUIRE(result.out.empty());
+}
+
+TEST_CASE("command::forkExec child exits 127 when shell exec fails", "[util][command]") {
+  const auto pid = waybar::util::command::forkExec("echo should-not-run", "test-output");
+  REQUIRE(pid > 0);
+
+  int status = -1;
+  REQUIRE(waitpid(pid, &status, 0) == pid);
+  REQUIRE(WIFEXITED(status));
+  REQUIRE(WEXITSTATUS(status) == waybar::util::command::kExecFailureExitCode);
+
+  std::scoped_lock<std::mutex> lock(reap_mtx);
+  reap.remove(pid);
+}

test/utils/meson.build

@@ -14,6 +14,7 @@ test_src = files(
     'JsonParser.cpp',
     'SafeSignal.cpp',
     'sleeper_thread.cpp',
+    'command.cpp',
     'css_reload_helper.cpp',
     '../../src/util/css_reload_helper.cpp',
 )