From 98c1d516b7f7624f7fcd7b9046783e3903a6a42b Mon Sep 17 00:00:00 2001
From: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Date: Fri, 28 Apr 2017 13:27:43 +0200
Subject: [PATCH] alloca: detect whether alloca.h exists

We can't depend on QT_HAS_INCLUDE for such an important functionality in
QtQml, so detect at configure time.

alloca() is not a POSIX function (it apparently first appeared in
Version 32V AT&T UNIX), so the actual header that defines it varies from
system to system. Clearly, if alloca.h exists, that's the one, so we try
it first. On most other systems that don't define it, it's in stdlib.h.
The only exception is Windows, where it's actually defined in malloc.h.

Task-number: QTBUG-59700
Started-by: Thiago Macieira <thiago.macieira@intel.com>
Change-Id: Icd0e0d4b27cb4e5eb892fffd14b4b2b389a4684e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
---
 config.tests/common/alloca/alloca.cpp     | 13 ++++++++---
 configure.json                            | 28 ++++++++++++++++++++---
 src/corelib/global/qconfig-bootstrapped.h |  7 ++++++
 3 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/config.tests/common/alloca/alloca.cpp b/config.tests/common/alloca/alloca.cpp
index d839b381ef1..500bdb9ba21 100644
--- a/config.tests/common/alloca/alloca.cpp
+++ b/config.tests/common/alloca/alloca.cpp
@@ -37,10 +37,17 @@
 **
 ****************************************************************************/
 
-#include <alloca.h>
-
+#if defined(USE_ALLOCA_H)
+# include <alloca.h>
+# ifdef __QNXNTO__
 // extra include needed in QNX7 to define NULL for the alloca() macro
-#include <stdlib.h>
+#  include <stddef.h>
+# endif
+#elif defined(USE_MALLOC_H)
+# include <malloc.h>
+#else
+# include <stdlib.h>
+#endif
 
 int main(int, char **)
 {
diff --git a/configure.json b/configure.json
index 49586ed6b8f..02d5f1a65ed 100644
--- a/configure.json
+++ b/configure.json
@@ -406,11 +406,23 @@
             "type": "compile",
             "test": "unix/posix_fallocate"
         },
-        "alloca": {
-            "label": "alloca()",
+        "alloca_stdlib_h": {
+            "label": "alloca() in stdlib.h",
             "type": "compile",
             "test": "common/alloca"
         },
+        "alloca_h": {
+            "label": "alloca() in alloca.h",
+            "type": "compile",
+            "test": "common/alloca",
+            "args": "DEFINES+=USE_ALLOCA_H"
+        },
+        "alloca_malloc_h": {
+            "label": "alloca() in malloc.h",
+            "type": "compile",
+            "test": "common/alloca",
+            "args": "DEFINES+=USE_MALLOC_H"
+        },
         "stack_protector": {
             "label": "stack protection",
             "type": "compilerSupportsFlag",
@@ -900,9 +912,19 @@
             "condition": "tests.posix_fallocate",
             "output": [ "privateFeature" ]
         },
+        "alloca_h": {
+            "label": "alloca.h",
+            "condition": "tests.alloca_h",
+            "output": [ "privateFeature" ]
+        },
+        "alloca_malloc_h": {
+            "label": "alloca() in malloc.h",
+            "condition": "!features.alloca_h && tests.alloca_malloc_h",
+            "output": [ "privateFeature" ]
+        },
         "alloca": {
             "label": "alloca()",
-            "condition": "tests.alloca",
+            "condition": "features.alloca_h || features.alloca_malloc_h || tests.alloca_stdlib_h",
             "output": [ "privateFeature" ]
         },
         "stack-protector-strong": {
diff --git a/src/corelib/global/qconfig-bootstrapped.h b/src/corelib/global/qconfig-bootstrapped.h
index bda8ad79168..0b02ecc8ec6 100644
--- a/src/corelib/global/qconfig-bootstrapped.h
+++ b/src/corelib/global/qconfig-bootstrapped.h
@@ -68,6 +68,13 @@
 
 #define QT_CRYPTOGRAPHICHASH_ONLY_SHA1
 #define QT_NO_DATASTREAM
+#define QT_FEATURE_alloca 1
+#define QT_FEATURE_alloca_h -1
+#ifdef _WIN32
+# define QT_FEATURE_alloca_malloc_h 1
+#else
+# define QT_FEATURE_alloca_malloc_h -1
+#endif
 #define QT_FEATURE_iconv -1
 #define QT_FEATURE_icu -1
 #define QT_FEATURE_journald -1