Add log framework

.github/copilot-instructions.md

@@ -31,3 +31,10 @@ Always check the `specs` directory.
 If there is anything unclear, ask the user for clarification.
 It is certainly possible that there are contradictions in the
 spec that have to be solved first.
+
+## Comitting
+Often, the user modifies an interface (typically in a header file), and then asks
+the agent to update the implementation.
+
+When creating a commit, make sure that both the user's and the agent's modifications
+are included in the commit.

v0/include.mk

@@ -1,4 +1,4 @@
-V0_SRC := v0/main.c v0/token.c v0/parser.c
+V0_SRC := v0/main.c v0/token.c v0/parser.c v0/log.c
 
 # V0_TEST must only include `v0/test.c` itself, as all other test C–source files are
 # included directly into `v0/test.c` using `#include "test_xyz.c"`.

v0/log.c

@@ -0,0 +1,16 @@
+#include "log.h"
+#include <stdio.h>
+
+static LogError* s_logError = NULL;
+
+void log_set_output(LogError* destination) {
+    s_logError = destination;
+}
+
+void log_error(const char* msg) {
+    if (s_logError != NULL) {
+        s_logError(msg);
+    } else {
+        fprintf(stderr, "Error: %s\n", msg);
+    }
+}

v0/log.h

@@ -0,0 +1,22 @@
+/**
+ * Contains the logging framework used for logging errors during compilation.
+ */
+#ifndef LOG_H
+#define LOG_H
+
+/**
+ * A method that can log an error.
+ */
+typedef void LogError(const char* msg);
+
+/**
+ * Sets the destination for log errors.
+ */
+void log_set_output(LogError* destination);
+
+/**
+ * Logs an error to the destination.
+ */
+void log_error(const char* msg);
+
+#endif

v0/test.c

@@ -30,6 +30,7 @@ typedef struct {
 
 #include "test_token.c"
 #include "test_parser.c"
+#include "test_log.c"
 
 static int s_totalTests;
 static int s_greenTests;
@@ -44,6 +45,7 @@ static TestCase s_tests[] = {
     {"tokenstream_void_function_signature", test_tokenstream_void_function_signature},
     {"tokenstream_info", test_tokenstream_info},
     {"parser_module_name", test_parser_module_name},
+    {"log_error", test_log_error},
 };
 
 

v0/test_log.c

@@ -0,0 +1,21 @@
+#include "test.h"
+#include "log.h"
+#include <string.h>
+
+static char s_lastLoggedError[256];
+
+static void mock_log(const char* msg) {
+    strncpy(s_lastLoggedError, msg, sizeof(s_lastLoggedError) - 1);
+    s_lastLoggedError[sizeof(s_lastLoggedError) - 1] = '\0';
+}
+
+static void test_log_error(void) {
+    log_set_output(mock_log);
+    
+    memset(s_lastLoggedError, 0, sizeof(s_lastLoggedError));
+    log_error("test error message");
+    
+    assert_str("test error message", s_lastLoggedError, "expected 'test error message'");
+
+    log_set_output(NULL); // Reset to default
+}