diff --git a/flang/include/flang/Runtime/extensions.h b/flang/include/flang/Runtime/extensions.h
index b34edb94ada43..d8ddd8069e202 100644
--- a/flang/include/flang/Runtime/extensions.h
+++ b/flang/include/flang/Runtime/extensions.h
@@ -33,7 +33,7 @@ void FORTRAN_PROCEDURE_NAME(getarg)(
     std::int32_t &n, std::int8_t *arg, std::int64_t length);
 
 // GNU extension subroutine GETLOG(C).
-void FORTRAN_PROCEDURE_NAME(getlog)(std::byte *name, std::int64_t length);
+void FORTRAN_PROCEDURE_NAME(getlog)(char *name, std::int64_t length);
 
 } // extern "C"
 #endif // FORTRAN_RUNTIME_EXTENSIONS_H_
diff --git a/flang/runtime/extensions.cpp b/flang/runtime/extensions.cpp
index 352da8f11d9d5..1b3ccc6c298ab 100644
--- a/flang/runtime/extensions.cpp
+++ b/flang/runtime/extensions.cpp
@@ -15,6 +15,7 @@
 #include "flang/Runtime/command.h"
 #include "flang/Runtime/descriptor.h"
 #include "flang/Runtime/io-api.h"
+#include "flang/Runtime/memory.h"
 #include <ctime>
 
 #ifdef _WIN32
@@ -47,8 +48,7 @@ extern "C" {
 
 namespace Fortran::runtime {
 
-void GetUsernameEnvVar(
-    const char *envName, std::byte *arg, std::int64_t length) {
+void GetUsernameEnvVar(const char *envName, char *arg, std::int64_t length) {
   Descriptor name{*Descriptor::Create(
       1, std::strlen(envName) + 1, const_cast<char *>(envName), 0)};
   Descriptor value{*Descriptor::Create(1, length, arg, 0)};
@@ -98,7 +98,7 @@ void FORTRAN_PROCEDURE_NAME(getarg)(
 }
 
 // CALL GETLOG(USRNAME)
-void FORTRAN_PROCEDURE_NAME(getlog)(std::byte *arg, std::int64_t length) {
+void FORTRAN_PROCEDURE_NAME(getlog)(char *arg, std::int64_t length) {
 #if _REENTRANT || _POSIX_C_SOURCE >= 199506L
   int nameMaxLen;
 #ifdef LOGIN_NAME_MAX
@@ -108,17 +108,19 @@ void FORTRAN_PROCEDURE_NAME(getlog)(std::byte *arg, std::int64_t length) {
   if (nameMaxLen == -1)
     nameMaxLen = _POSIX_LOGIN_NAME_MAX + 1;
 #endif
-  std::vector<char> str(nameMaxLen);
+  Terminator terminator{__FILE__, __LINE__};
+  char *str{static_cast<char *>(AllocateMemoryOrCrash(terminator, nameMaxLen))};
+  str[nameMaxLen] = '\0';
 
-  int error{getlogin_r(str.data(), nameMaxLen)};
+  int error{getlogin_r(str, nameMaxLen)};
   if (error == 0) {
     // no error: find first \0 in string then pad from there
-    CopyAndPad(reinterpret_cast<char *>(arg), str.data(), length,
-        std::strlen(str.data()));
+    CopyAndPad(arg, str, length, std::strlen(str));
   } else {
     // error occur: get username from environment variable
     GetUsernameEnvVar("LOGNAME", arg, length);
   }
+  FreeMemory((void *)str);
 #elif _WIN32
   // Get username from environment to avoid link to Advapi32.lib
   GetUsernameEnvVar("USERNAME", arg, length);
diff --git a/flang/unittests/Runtime/CommandTest.cpp b/flang/unittests/Runtime/CommandTest.cpp
index a0f14c519412a..c0c0b21556e82 100644
--- a/flang/unittests/Runtime/CommandTest.cpp
+++ b/flang/unittests/Runtime/CommandTest.cpp
@@ -9,10 +9,12 @@
 #include "flang/Runtime/command.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "../../runtime/terminator.h"
 #include "flang/Runtime/descriptor.h"
 #include "flang/Runtime/execute.h"
 #include "flang/Runtime/extensions.h"
 #include "flang/Runtime/main.h"
+#include "flang/Runtime/memory.h"
 #include <cstddef>
 #include <cstdlib>
 
@@ -682,8 +684,7 @@ TEST_F(EnvironmentVariables, GetlogGetName) {
   const int charLen{3};
   char input[charLen]{"\0\0"};
 
-  FORTRAN_PROCEDURE_NAME(getlog)
-  (reinterpret_cast<std::byte *>(input), charLen);
+  FORTRAN_PROCEDURE_NAME(getlog)(input, charLen);
 
   EXPECT_NE(input[0], '\0');
 }
@@ -699,12 +700,13 @@ TEST_F(EnvironmentVariables, GetlogPadSpace) {
   if (charLen == -1)
     charLen = _POSIX_LOGIN_NAME_MAX + 2;
 #endif
-  std::vector<char> input(charLen);
+  Terminator terminator{__FILE__, __LINE__};
+  char *input{(char *)AllocateMemoryOrCrash(terminator, charLen)};
 
-  FORTRAN_PROCEDURE_NAME(getlog)
-  (reinterpret_cast<std::byte *>(input.data()), charLen);
+  FORTRAN_PROCEDURE_NAME(getlog)(input, charLen);
 
   EXPECT_EQ(input[charLen - 1], ' ');
+  FreeMemory((void *)input);
 }
 #endif
 
@@ -715,8 +717,7 @@ TEST_F(EnvironmentVariables, GetlogEnvGetName) {
         << "Environment variable USERNAME does not exist";
 
     char input[]{"XXXXXXXXX"};
-    FORTRAN_PROCEDURE_NAME(getlog)
-    (reinterpret_cast<std::byte *>(input), sizeof(input));
+    FORTRAN_PROCEDURE_NAME(getlog)(input, sizeof(input));
 
     CheckCharEqStr(input, "loginName");
   }
@@ -728,8 +729,7 @@ TEST_F(EnvironmentVariables, GetlogEnvBufferShort) {
         << "Environment variable USERNAME does not exist";
 
     char input[]{"XXXXXX"};
-    FORTRAN_PROCEDURE_NAME(getlog)
-    (reinterpret_cast<std::byte *>(input), sizeof(input));
+    FORTRAN_PROCEDURE_NAME(getlog)(input, sizeof(input));
 
     CheckCharEqStr(input, "loginN");
   }
@@ -741,8 +741,7 @@ TEST_F(EnvironmentVariables, GetlogEnvPadSpace) {
         << "Environment variable USERNAME does not exist";
 
     char input[]{"XXXXXXXXXX"};
-    FORTRAN_PROCEDURE_NAME(getlog)
-    (reinterpret_cast<std::byte *>(input), sizeof(input));
+    FORTRAN_PROCEDURE_NAME(getlog)(input, sizeof(input));
 
     CheckCharEqStr(input, "loginName ");
   }