libfuzzer: log all the libcalls to stderr

lib/fuzzer.zig

@@ -9,3 +9,54 @@ export fn __sanitizer_cov_8bit_counters_init(start: [*]u8, stop: [*]u8) void {
 export fn __sanitizer_cov_pcs_init(pcs_beg: [*]const usize, pcs_end: [*]const usize) void {
     std.debug.print("__sanitizer_cov_pcs_init pcs_beg={*}, pcs_end={*}\n", .{ pcs_beg, pcs_end });
 }
+
+export fn __sanitizer_cov_trace_const_cmp1(arg1: u8, arg2: u8) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_cmp1(arg1: u8, arg2: u8) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_const_cmp2(arg1: u16, arg2: u16) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_cmp2(arg1: u16, arg2: u16) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_const_cmp4(arg1: u32, arg2: u32) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_cmp4(arg1: u32, arg2: u32) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_const_cmp8(arg1: u64, arg2: u64) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_cmp8(arg1: u64, arg2: u64) void {
+    handleCmp(@returnAddress(), arg1, arg2);
+}
+
+export fn __sanitizer_cov_trace_switch(val: u64, cases_ptr: [*]u64) void {
+    const pc = @returnAddress();
+    const len = cases_ptr[0];
+    const val_size_in_bits = cases_ptr[1];
+    const cases = cases_ptr[2..][0..len];
+    std.debug.print("0x{x}: switch on value {d} ({d} bits) with {d} cases\n", .{
+        pc, val, val_size_in_bits, cases.len,
+    });
+}
+
+export fn __sanitizer_cov_trace_pc_indir(callee: usize) void {
+    const pc = @returnAddress();
+    std.debug.print("0x{x}: indirect call to 0x{x}\n", .{ pc, callee });
+}
+
+fn handleCmp(pc: usize, arg1: u64, arg2: u64) void {
+    std.debug.print("0x{x}: comparison of {d} and {d}\n", .{ pc, arg1, arg2 });
+}