From 062c1a54b295b4ff387ebdff84a6a957fccbefd4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C4=90o=C3=A0n=20Tr=E1=BA=A7n=20C=C3=B4ng=20Danh?=
 <congdanhqx@gmail.com>
Date: Sun, 17 May 2020 22:44:25 +0700
Subject: [PATCH 5/7] libevent: use compile time sizeof check

Taken from https://github.com/scons/scons/wiki/AutoconfRecipes#ac_check_sizeof
---
 src/libevent/SConscript | 81 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 73 insertions(+), 8 deletions(-)

diff --git src/libevent/SConscript src/libevent/SConscript
index 1197b8d3..ab1f72ad 100644
--- src/libevent/SConscript
+++ src/libevent/SConscript
@@ -18,22 +18,87 @@ conf.AddTest('CheckSYS_TIMERFD_H', CheckSYS_TIMERFD_H)
 
 
 # sizeof
+# https://github.com/scons/scons/wiki/AutoconfRecipes#ac_check_sizeof
+# Sensible default for common types on common platforms.
+_DEFAULTS_SIZEOF = {
+    'short' : [2],
+    'int' : [4, 2],
+    'long' : [4, 8],
+    'long long' : [8, 4],
+    'unsigned short' : [2],
+    'unsigned int' : [4, 2],
+    'unsigned long' : [4, 8],
+    'unsigned long long' : [8, 4],
+    'float' : [4],
+    'double' : [8],
+    'long double' : [12],
+    'size_t' : [4, 8],
+}
+
 def CheckSizeOf(ctx, type, includes = None):
+    """This check can be used to get the size of a given type,
+    or to check whether the type is of expected size.
+
+    Arguments:
+        - type : str
+            the type to check
+        - includes : sequence
+            list of headers to include in the test code before testing the type
+        Returns:
+                status : int
+                        0 if the check failed, or the found size of the type
+                        if the check succeeded."""
+    minsz = 0
+    maxsz = 16
+
     src = '''
       #include <sys/types.h>
       #include <stdlib.h>
       #include <stdio.h>
-      int main() {printf("%d", (int)sizeof(''' + type + ''')); return 0;}
+      #include <stdint.h>
     '''
+    if includes:
+        src += "\n".join("#include <%s>\n" % i for i in includes)
 
-    if includes is not None:
-        for inc in includes:
-            src = '#include <%s>\n%s' % (inc, src)
+    ext = '.c'
+    # test code taken from autoconf: this is a pretty clever hack to find that
+    # a type is of a given size using only compilation. This speeds things up
+    # quite a bit compared to straightforward code using TryRun
+    src += r"""
+typedef %s scons_check_type;
 
-    ctx.Message('Checking size of ' + type + '... ')
-    ret = ctx.TryRun(src + '\n', '.c')
-    ctx.Result(ret[0])
-    return ret[1]
+int main()
+{
+    static int test_array[1 - 2 * ((long int) sizeof(scons_check_type) > %d)];
+    test_array[0] = 0;
+
+    return 0;
+}
+"""
+
+    # Only check if the given size is the right one
+    ctx.Message('Checking size of %s ... ' % type)
+
+    # Try sensible defaults first
+    try:
+        szrange = _DEFAULTS_SIZEOF[type]
+    except KeyError:
+        szrange = []
+    szrange.extend(range(minsz, maxsz))
+    st = 0
+
+    # Actual test
+    for sz in szrange:
+        st = ctx.TryCompile(src % (type, sz), ext)
+        if st:
+            break
+
+    if st:
+        ctx.Result('%d' % sz)
+        return sz
+    else:
+        ctx.Result('Failed !')
+        return 0
 
 conf.AddTest('CheckSizeOf', CheckSizeOf)
 
-- 
2.27.0.rc1.5.gae92ac8ae3