Add an example program in C

.gitignore

@@ -18,3 +18,4 @@ CTestTestfile.cmake
 Testing
 result
 build
+example/example

example/Makefile

@@ -0,0 +1,2 @@
+example: example.c
+	riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -o example example.c -T linker.ld

example/example.c

@@ -0,0 +1,9 @@
+static int mem;
+
+int main() {
+  int a = 42;
+  int b = 5;
+  mem = a*b + 3;
+
+  return 0;
+}

example/linker.ld

@@ -0,0 +1,19 @@
+ENTRY(_start)
+
+SECTIONS {
+    . = 0x1000;  /* Start address of the program */
+
+    .text : {
+        *(.text)   /* Place all .text sections (code) here */
+    }
+
+    .data : {
+        *(.data)   /* Place all .data sections (initialized data) here */
+    }
+
+    .bss : {
+        *(.bss)    /* Place all .bss sections (uninitialized data) here */
+    }
+
+    /DISCARD/ : { *(.note.GNU-stack) }  /* Discard stack section */
+}

flake.nix

@@ -21,16 +21,22 @@
       forAllSystems = f: nixpkgs.lib.genAttrs allSystems (system: f {
         pkgs = import nixpkgs { inherit system; };
       });
+      riscv-pkgs = import nixpkgs {
+        localSystem = "x86_64-linux";
+        crossSystem = {
+          config = "riscv32-unknown-linux-gnu";
+        };
+      };
     in
       {
-        packages = forAllSystems( {pkgs }:
+        packages = forAllSystems( {pkgs}:
           {
-            lisp = (pkgs.callPackage ./rve.nix {});
+            lisp = (pkgs.callPackage ./rve.nix {riscv-pkgs=riscv-pkgs;});
-            default = (pkgs.callPackage ./rve.nix {});
+            default = (pkgs.callPackage ./rve.nix {riscv-pkgs=riscv-pkgs;});
           }
         );
         overlays.default = final: prev: {
-          lisp = (prev.callPackage ./rve.nix {});
+          lisp = (prev.callPackage ./rve.nix {riscv-pkgs=riscv-pkgs;});
         };
       };
 }

rve.nix

@@ -1,4 +1,4 @@
-{ pkgs, stdenv }:
+{ pkgs, stdenv, riscv-pkgs }:
 pkgs.gcc13Stdenv.mkDerivation rec {
   pname = "rve";
   version = "0.1.0";
@@ -13,7 +13,15 @@ pkgs.gcc13Stdenv.mkDerivation rec {
 
   nativeBuildInputs = with pkgs; [ pkg-config cmake ninja ];
 
-  buildInputs = with pkgs; [ gdb linuxPackages.perf jq lcov ];
+  buildInputs = with pkgs; [
+    gdb
+    linuxPackages.perf
+    jq
+    lcov
+    #riscv-pkgs.buildPackages.gcc
+    pkgsCross.riscv32-embedded.buildPackages.gcc
+    pkgsCross.riscv32-embedded.buildPackages.binutils
+  ];
 
   hardeningDisable = [ "all" ];
   cmakeFlags = [

src/rve.cpp

@@ -5,7 +5,7 @@
 #include <cstring>
 
 int main() {
-  const size_t MEMORY_SIZE = 1024;
+  const size_t MEMORY_SIZE = 128*1024;
   uint8_t memory[MEMORY_SIZE] = {0};
 
   uint32_t program[] = {