From ad430c0daad16019a6c440ab735a61856523329a Mon Sep 17 00:00:00 2001
From: Jacek Sieka <arnetheduck@gmail.com>
Date: Thu, 30 Jun 2022 10:20:19 +0200
Subject: once C++, always C++ [backport] (#19938)

* once C++, always C++

When using `{.compile: "file.cc".}` in a nim module, even when compiling
with `nim c` the C++ compiler should be used - once any C++ file has
been compiled, the C++ linker also needs to be used.

* more strict C++ check

* simplify code
---
 compiler/extccomp.nim | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

(limited to 'compiler/extccomp.nim')

diff --git a/compiler/extccomp.nim b/compiler/extccomp.nim
index 5c074d284..f1dc01f44 100644
--- a/compiler/extccomp.nim
+++ b/compiler/extccomp.nim
@@ -493,7 +493,10 @@ proc needsExeExt(conf: ConfigRef): bool {.inline.} =
            (conf.target.hostOS == osWindows)
 
 proc useCpp(conf: ConfigRef; cfile: AbsoluteFile): bool =
-  conf.backend == backendCpp and not cfile.string.endsWith(".c")
+  # List of possible file extensions taken from gcc
+  for ext in [".C", ".cc", ".cpp", ".CPP", ".c++", ".cp", ".cxx"]:
+    if cfile.string.endsWith(ext): return true
+  false
 
 proc envFlags(conf: ConfigRef): string =
   result = if conf.backend == backendCpp:
@@ -501,14 +504,14 @@ proc envFlags(conf: ConfigRef): string =
           else:
             getEnv("CFLAGS")
 
-proc getCompilerExe(conf: ConfigRef; compiler: TSystemCC; cfile: AbsoluteFile): string =
+proc getCompilerExe(conf: ConfigRef; compiler: TSystemCC; isCpp: bool): string =
   if compiler == ccEnv:
-    result = if useCpp(conf, cfile):
+    result = if isCpp:
               getEnv("CXX")
             else:
               getEnv("CC")
   else:
-    result = if useCpp(conf, cfile):
+    result = if isCpp:
               CC[compiler].cppCompiler
             else:
               CC[compiler].compilerExe
@@ -547,22 +550,25 @@ proc ccHasSaneOverflow*(conf: ConfigRef): bool =
 
 proc getLinkerExe(conf: ConfigRef; compiler: TSystemCC): string =
   result = if CC[compiler].linkerExe.len > 0: CC[compiler].linkerExe
-           elif optMixedMode in conf.globalOptions and conf.backend != backendCpp: CC[compiler].cppCompiler
-           else: getCompilerExe(conf, compiler, AbsoluteFile"")
+           else: getCompilerExe(conf, compiler, optMixedMode in conf.globalOptions or conf.backend == backendCpp)
 
 proc getCompileCFileCmd*(conf: ConfigRef; cfile: Cfile,
                          isMainFile = false; produceOutput = false): string =
-  let c = conf.cCompiler
+  let
+    c = conf.cCompiler
+    isCpp = useCpp(conf, cfile.cname)
   # We produce files like module.nim.cpp, so the absolute Nim filename is not
   # cfile.name but `cfile.cname.changeFileExt("")`:
   var options = cFileSpecificOptions(conf, cfile.nimname, cfile.cname.changeFileExt("").string)
-  if useCpp(conf, cfile.cname):
+  if isCpp:
     # needs to be prepended so that --passc:-std=c++17 can override default.
     # we could avoid allocation by making cFileSpecificOptions inplace
     options = CC[c].cppXsupport & ' ' & options
+    # If any C++ file was compiled, we need to use C++ driver for linking as well
+    incl conf.globalOptions, optMixedMode
 
   var exe = getConfigVar(conf, c, ".exe")
-  if exe.len == 0: exe = getCompilerExe(conf, c, cfile.cname)
+  if exe.len == 0: exe = getCompilerExe(conf, c, isCpp)
 
   if needsExeExt(conf): exe = addFileExt(exe, "exe")
   if (optGenDynLib in conf.globalOptions or (conf.hcrOn and not isMainFile)) and
@@ -582,7 +588,7 @@ proc getCompileCFileCmd*(conf: ConfigRef; cfile: Cfile,
 
     compilePattern = joinPath(conf.cCompilerPath, exe)
   else:
-    compilePattern = getCompilerExe(conf, c, cfile.cname)
+    compilePattern = getCompilerExe(conf, c, isCpp)
 
   includeCmd.add(join([CC[c].includeCmd, quoteShell(conf.projectPath.string)]))
 
-- 
cgit 1.4.1-2-gfad0