[cpp] on windows, whenever you invoke a linker/archiver, it will firs…

…t attempt to find and call vcvars64.bat. this should fail silently if you dont have visual studio iinstalled (although will instead fail to find link.exe). in this case, you should explicitly specify the linker you want via -l. this means that you can now use visual studio stuff with psyc and it will automatically call vcvarsxyz.bat instead of you having to do it in a vc terminal

cpp/src/link.cpp

@@ -1,5 +1,6 @@
 #include "link.hpp"
 #include "diag.hpp"
+#include <array>
 
 namespace link
 {
@@ -85,6 +86,56 @@ namespace link
 		}
 	}
 
+	std::string exec_windows(std::string_view cmd)
+	{
+		#ifdef _WIN32
+		std::array<char, 128> buffer;
+		std::string result;
+		std::unique_ptr<FILE, decltype(&_pclose)> pipe(_popen(cmd.data(), "r"), _pclose);
+		if (!pipe) {
+			return "";
+		}
+		while (fgets(buffer.data(), static_cast<int>(buffer.size()), pipe.get()) != nullptr) {
+			result += buffer.data();
+		}
+		return result;
+
+		#else
+
+		return "";
+		#endif
+	}
+
+	std::string replace_all(std::string str, const std::string& from, const std::string& to) {
+		size_t start_pos = 0;
+		while((start_pos = str.find(from, start_pos)) != std::string::npos) {
+			str.replace(start_pos, from.length(), to);
+			start_pos += to.length(); // Handles case where 'to' is a substring of 'from'
+		}
+		return str;
+	}
+
+	std::string get_linker_prefix()
+	{
+		// if we're on win32, we will need to invoke vcvars64.bat first.
+		// let's get that.
+		#ifdef _WIN32
+
+		std::string root_path = exec_windows("\"\"C:/Program Files (x86)/Microsoft Visual Studio/Installer/vswhere.exe\" -latest -products * -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 | findstr \"installationPath\"");
+		if(root_path.empty())
+		{
+			return "";
+		}
+
+		root_path.erase(0, sizeof("installationPath:"));
+		std::string vcvarsall_path = replace_all(root_path + "\\VC\\Auxiliary\\Build\\vcvars64.bat", "\n", "");
+		vcvarsall_path = "\"\"" + vcvarsall_path + "\" && ";
+		return vcvarsall_path;
+		#else
+		return "";
+		#endif
+	}
+
 	void executable(std::vector<std::filesystem::path> object_files, std::filesystem::path output_path, std::string output_name, std::string linker)
 	{
 		if(linker.empty())
@@ -109,6 +160,7 @@ namespace link
 			break;
 			case linker_type::msvc:
 				cmd += std::format( " /OUT:\"{}\"", full_output);
+				cmd = get_linker_prefix() + cmd;
 			break;
 		}
 
@@ -135,6 +187,7 @@ namespace link
 			break;
 			case linker_type::msvc:
 				cmd += std::format( " /OUT:\"{}\"", full_output);
+				cmd = get_linker_prefix() + cmd;
 			break;
 		}