From c419ece7cde4e395c813545243fc54b9936457db Mon Sep 17 00:00:00 2001
From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Thu, 19 Jan 2023 16:11:06 +0100
Subject: [PATCH] doctest: make the "Exporting a C Library" example work

The mathtest example of exporting a library with the C ABI it not
working, since the mathtest.h file is not generated.

Update the shell sample, adding the -femit-h flag to the zig build-lib
command.

Show an example of how to copy the zig.h file to the project directory,
using zig env and jq.  I'm not sure if there is a better/official
method.
---
 doc/langref.html.in | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/doc/langref.html.in b/doc/langref.html.in
index 30dbbb604e5d..493703548612 100644
--- a/doc/langref.html.in
+++ b/doc/langref.html.in
@@ -10901,9 +10901,15 @@ export fn add(a: i32, b: i32) i32 {
 }
       {#code_end#}
       <p>To make a static library:</p>
-      {#shell_samp#}$ zig build-lib mathtest.zig{#end_shell_samp#}
+      {#shell_samp#}$ zig build-lib -femit-h mathtest.zig{#end_shell_samp#}
       <p>To make a shared library:</p>
-      {#shell_samp#}$ zig build-lib mathtest.zig -dynamic{#end_shell_samp#}
+      {#shell_samp#}$ zig build-lib -femit-h mathtest.zig -dynamic{#end_shell_samp#}
+      <p>
+      The <kbd>-femit-h</kbd> flag is necessary in order to generate the mathtest.h file.
+      The generated C header file includes the zig.h file that must be copied
+      to the project directory, as an example using <a href="https://stedolan.github.io/jq/">jq</a>:
+      </p>
+      {#shell_samp#}cp $(zig env | jq -r .lib_dir)/zig.h .{#end_shell_samp#}
       <p>Here is an example with the {#link|Zig Build System#}:</p>
       {#syntax_block|c|test.c#}// This header is generated by zig from mathtest.zig
 #include "mathtest.h"