julia: support clang, set llvm NDEBUG correctly (#30800)

var/spack/repos/builtin/packages/julia/gcc-ifdef.patch

@@ -0,0 +1,25 @@
+From 3193c8f2596711c1feb8e655ec391050e0e78ed0 Mon Sep 17 00:00:00 2001
+From: Harmen Stoppels <harmenstoppels@gmail.com>
+Date: Mon, 23 May 2022 16:58:23 +0200
+Subject: [PATCH] Guard GCC-specific macros with _COMPILER_GCC_
+
+---
+ src/julia_internal.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/julia_internal.h b/src/julia_internal.h
+index fbded19..32d038b 100644
+--- a/src/julia_internal.h
++++ b/src/julia_internal.h
+@@ -392,7 +392,7 @@ jl_svec_t *jl_perm_symsvec(size_t n, ...);
+ 
+ // this sizeof(__VA_ARGS__) trick can't be computed until C11, but that only matters to Clang in some situations
+ #if !defined(__clang_analyzer__) && !(defined(JL_ASAN_ENABLED) || defined(JL_TSAN_ENABLED))
+-#ifdef __GNUC__
++#ifdef _COMPILER_GCC_
+ #define jl_perm_symsvec(n, ...) \
+     (jl_perm_symsvec)(__extension__({                                         \
+             static_assert(                                                    \
+-- 
+2.25.1
+

var/spack/repos/builtin/packages/julia/llvm-NDEBUG.patch

@@ -0,0 +1,30 @@
+From 4ec1970178606127fd8bbffa763f135ca0f12ee3 Mon Sep 17 00:00:00 2001
+From: Harmen Stoppels <harmenstoppels@gmail.com>
+Date: Tue, 24 May 2022 14:03:48 +0200
+Subject: [PATCH] llvm: add NDEBUG when assertion mode is off
+
+`llvm-config --cxxflags` unfortunately does not set `-DNDEBUG`, which
+Julia needs to set correctly when including LLVM header files.
+---
+ src/Makefile | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/src/Makefile b/src/Makefile
+index 1a9af2fa7c..766fd2945f 100644
+--- a/src/Makefile
++++ b/src/Makefile
+@@ -98,6 +98,11 @@ PUBLIC_HEADER_TARGETS := $(addprefix $(build_includedir)/julia/,$(notdir $(PUBLI
+ LLVM_LDFLAGS := $(shell $(LLVM_CONFIG_HOST) --ldflags)
+ LLVM_CXXFLAGS := $(shell $(LLVM_CONFIG_HOST) --cxxflags)
+ 
++# llvm-config --cxxflags does not return -DNDEBUG
++ifeq ($(shell $(LLVM_CONFIG_HOST) --assertion-mode),OFF)
++LLVM_CXXFLAGS += -DNDEBUG
++endif
++
+ ifeq ($(JULIACODEGEN),LLVM)
+ ifneq ($(USE_SYSTEM_LLVM),0)
+ LLVMLINK += $(LLVM_LDFLAGS) $(shell $(LLVM_CONFIG_HOST) --libs --system-libs)
+-- 
+2.25.1
+

var/spack/repos/builtin/packages/julia/package.py

@@ -130,6 +130,12 @@ class Julia(MakefilePackage):
     # only applied to libllvm when it's vendored by julia).
     patch('revert-fix-rpath-of-libllvm.patch', when='@1.7.0:1.7')
 
+    # Allow build with clang.
+    patch('gcc-ifdef.patch', when='@1.7.0:1.7')
+
+    # Make sure Julia sets -DNDEBUG when including LLVM header files.
+    patch('llvm-NDEBUG.patch', when='@1.7.0:1.7')
+
     def patch(self):
         # The system-libwhich-libblastrampoline.patch causes a rebuild of docs as it
         # touches the main Makefile, so we reset the a/m-time to doc/_build's.
@@ -215,6 +221,9 @@ def edit(self, spec, prefix):
                 '1' if spec.variants['precompile'].value else '0'),
         ]
 
+        options.append('USEGCC:={}'.format('1' if '%gcc' in spec else '0'))
+        options.append('USECLANG:={}'.format('1' if '%clang' in spec else '0'))
+
         # libm or openlibm?
         if spec.variants['openlibm'].value:
             options.append('USE_SYSTEM_LIBM=0')