[lmi-commits] [lmi] master fea5864 2/2: Prefer modern dialect

[Greg Chicares]

branch: master
commit fea586445727a91df76ccc2eafd36b15c0b972e6
Author: Gregory W. Chicares <address@hidden>
Commit: Gregory W. Chicares <address@hidden>

    Prefer modern dialect
    
    It's not necessarily obvious why the non-const std::string::data()
    overload must return a contiguous, null-terminated C string. It's
    contiguous because C++17 (N4659) [24.3.2.7.1/4] says it returns
    | A pointer p such that
    | p + i == &operator[](i) for each i in [0, size()]
    ; and it's null-terminated because that range includes its right
    endpoint, and [24.3.2.5/2] operator[size()] returns charT(), which
    equals zero.
    
    Before C++17 added the non-const data() overload, some authors had
    recommended '&s[0]' instead of 's.data()'. The latter seems better
    for the same reason that 's.front()' is better than 's[0]'; moreover,
    '&s[0]' has been reported to elicit compiler warnings where '&s[0U]'
    does not.
    
    It's worth mentioning that, while
        STARTUPINFO startup_info = {};
    is fine, these alternatives:
        STARTUPINFO startup_info = {'\0'};
        STARTUPINFO startup_info = {0};
    elicit diagnostics from gcc-7.2.0 with '-Wall -Wextra':
      error: missing initializer for member...
      [-Werror=missing-field-initializers]
---
 system_command_non_wx.cpp | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/system_command_non_wx.cpp b/system_command_non_wx.cpp
index c38ca0b..09098d8 100644
--- a/system_command_non_wx.cpp
+++ b/system_command_non_wx.cpp
@@ -26,15 +26,9 @@
 #include "alert.hpp"
 
 #if !defined LMI_MSW
-
-#   include <cstdlib>
-
+#   include <cstdlib>                   // system()
 #else  // defined LMI_MSW
-
 #   include <windows.h>
-
-#   include <cstring>
-
 #endif // defined LMI_MSW
 
 namespace
@@ -61,17 +55,21 @@ void concrete_system_command(std::string const& 
command_line)
 
 void concrete_system_command(std::string const& command_line)
 {
-    STARTUPINFO startup_info;
-    std::memset(&startup_info, 0, sizeof(STARTUPINFO));
+    STARTUPINFO startup_info = {};
     startup_info.cb = sizeof(STARTUPINFO);
 
     PROCESS_INFORMATION process_info;
 
-    char* non_const_cmd_line_copy = new char[1 + command_line.size()];
-    std::strcpy(non_const_cmd_line_copy, command_line.c_str());
+    // For 'wine' at least, this argument cannot be const, even though
+    // this authority:
+    //   https://blogs.msdn.microsoft.com/oldnewthing/20090601-00/?p=18083
+    // says that requirement affects "only the Unicode version". It
+    // would seem wrong to change this wrapper's argument type (for
+    // POSIX too) because of this msw implementation detail.
+    std::string non_const_cmd_line_copy = command_line;
     ::CreateProcessA
         (0
-        ,non_const_cmd_line_copy
+        ,non_const_cmd_line_copy.data()
         ,0
         ,0
         ,true
@@ -81,7 +79,6 @@ void concrete_system_command(std::string const& command_line)
         ,&startup_info
         ,&process_info
         );
-    delete[]non_const_cmd_line_copy;
 
     DWORD exit_code = 12345;
     ::CloseHandle(process_info.hThread);