building a c/c++ file with `zig build-exe` no longer enables stack-protector

[xxxbxxx]

Zig Version

0.12.0-dev.1585+5a91e94ef0

Steps to Reproduce and Observed Behavior

when compiling a c or c++ file, the stack-protector is no longer enabled
since 53f74d6 "move libssp into libcompiler_rt "

zig build-exe main.c -lc --verbose-cc
-> zig clang main.c [....] -fsanitize-trap=undefined -fno-sanitize=function -mred-zone -fno-omit-frame-pointer -fno-stack-protector -D_DEBUG -O0 [...]

(note that zig build-exe main.c -lc -fllvm does restore the previous behaviour)

Expected Behavior

zig build-exe main.c -lc --verbose-cc
-> zig clang main.c [....] -fsanitize-trap=undefined -fno-sanitize=function -mred-zone -fno-omit-frame-pointer -fstack-protector-strong --param ssp-buffer-size=4 -D_DEBUG -O0 [...]

[xxxbxxx]

two questions:

• it is not clear to me whether -fllvm should be required for enabling compilation with clang ?
• if it is not required, what is supposed to happen when invoking zig build-exe main.zig other.cpp where the zig file is built with the selfhosted backend that doesn't support stackprotector and the extra other.cpp file that is built with clang?

maybe the fix is that, if unspecified, enable_llvm should be turned on as soon as there are some c/cpp files to compile?

[xxxbxxx]

proposed fix, no idea if it's the correct approch:

diff --git a/src/Compilation.zig b/src/Compilation.zig
index ed00734860..cf0783b924 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -1090,6 +1090,17 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation {
         const comp = try arena.create(Compilation);
         const root_name = try arena.dupeZ(u8, options.root_name);
 
+        // Make a decision on whether to use Clang or Aro for translate-c and compiling C files.
+        const c_frontend: CFrontend = blk: {
+            if (options.use_clang) |want_clang| {
+                break :blk if (want_clang) .clang else .aro;
+            }
+            break :blk if (build_options.have_llvm) .clang else .aro;
+        };
+        if (!build_options.have_llvm and c_frontend == .clang) {
+            return error.ZigCompilerNotBuiltWithLLVMExtensions;
+        }
+
         // Make a decision on whether to use LLVM or our own backend.
         const use_lib_llvm = options.use_lib_llvm orelse build_options.have_llvm;
         const use_llvm = blk: {
@@ -1118,6 +1129,10 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation {
             if (options.optimize_mode != .Debug)
                 break :blk true;
 
+            // If clang is requested for compilation of c/c++ files.
+            if (options.c_source_files.len != 0 and c_frontend == .clang)
+                break :blk true;
+
             // At this point we would prefer to use our own self-hosted backend,
             // because the compilation speed is better than LLVM. But only do it if
             // we are confident in the robustness of the backend.
@@ -1327,17 +1342,6 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation {
             break :pic explicit;
         } else pie or must_pic;
 
-        // Make a decision on whether to use Clang or Aro for translate-c and compiling C files.
-        const c_frontend: CFrontend = blk: {
-            if (options.use_clang) |want_clang| {
-                break :blk if (want_clang) .clang else .aro;
-            }
-            break :blk if (build_options.have_llvm) .clang else .aro;
-        };
-        if (!build_options.have_llvm and c_frontend == .clang) {
-            return error.ZigCompilerNotBuiltWithLLVMExtensions;
-        }
-
         const is_safe_mode = switch (options.optimize_mode) {
             .Debug, .ReleaseSafe => true,
             .ReleaseFast, .ReleaseSmall => false,

[xxxbxxx]

same problem as #18009