From 66d7370facc63648eb85fb7f1b94753ab0823ff3 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Fri, 13 Mar 2020 23:59:36 -0400
Subject: [PATCH] special case when doing build-obj with just one source file

When building an object file from only one source file, instead of
having a two-stage cache system, we special case it and use the cache
directory that the .o file is output to as the final cache directory for
all the build artifacts.

When there are more than 1 source file, the linker has to merge objects
into one, and so the two stage approach makes sens. But in the case of
only one source file, this prevents needlessly copying the object file.

This commit fixes an issue with the previous one, where zig with cache
enabled would print a directory that actually did not have any build
artifacts in it.
---
 src/codegen.cpp | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/codegen.cpp b/src/codegen.cpp
index aba8a49032..924ea9baa6 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -10482,10 +10482,6 @@ static void resolve_out_paths(CodeGen *g) {
             case OutTypeUnknown:
                 zig_unreachable();
             case OutTypeObj:
-                if (g->enable_cache && g->link_objects.length == 1 && !need_llvm_module(g)) {
-                    buf_init_from_buf(&g->bin_file_output_path, g->link_objects.at(0));
-                    return;
-                }
                 if (need_llvm_module(g) && g->link_objects.length != 0 && !g->enable_cache &&
                     buf_eql_buf(o_basename, out_basename))
                 {
@@ -10580,6 +10576,20 @@ static void output_type_information(CodeGen *g) {
     }
 }
 
+static bool main_output_dir_is_just_one_c_object(CodeGen *g) {
+    return g->enable_cache && g->link_objects.length == 1 && !need_llvm_module(g);
+}
+
+static void init_output_dir(CodeGen *g, Buf *digest) {
+    if (main_output_dir_is_just_one_c_object(g)) {
+        g->output_dir = buf_alloc();
+        os_path_dirname(g->link_objects.at(0), g->output_dir);
+    } else {
+        g->output_dir = buf_sprintf("%s" OS_SEP CACHE_OUT_SUBDIR OS_SEP "%s",
+            buf_ptr(g->cache_dir), buf_ptr(digest));
+    }
+}
+
 void codegen_build_and_link(CodeGen *g) {
     Error err;
     assert(g->out_type != OutTypeUnknown);
@@ -10622,8 +10632,7 @@ void codegen_build_and_link(CodeGen *g) {
     }
 
     if (g->enable_cache && buf_len(&digest) != 0) {
-        g->output_dir = buf_sprintf("%s" OS_SEP CACHE_OUT_SUBDIR OS_SEP "%s",
-                buf_ptr(g->cache_dir), buf_ptr(&digest));
+        init_output_dir(g, &digest);
         resolve_out_paths(g);
     } else {
         if (need_llvm_module(g)) {
@@ -10644,8 +10653,7 @@ void codegen_build_and_link(CodeGen *g) {
                     exit(1);
                 }
             }
-            g->output_dir = buf_sprintf("%s" OS_SEP CACHE_OUT_SUBDIR OS_SEP "%s",
-                    buf_ptr(g->cache_dir), buf_ptr(&digest));
+            init_output_dir(g, &digest);
 
             if ((err = os_make_path(g->output_dir))) {
                 fprintf(stderr, "Unable to create output directory: %s\n", err_str(err));