Use C99 VLA instead of alloca when available

4 files changed, 39 insertions, 19 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d80fbfcc..37aa57dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -159,6 +159,17 @@ IF(CMAKE_COMPILER_IS_GNUCC)
     SET(CMAKE_REQUIRED_FLAGS "${OLD_REQUIRED_FLAGS}")
 ENDIF()
 
+# Check if we have C99 variable length arrays
+CHECK_C_SOURCE_COMPILES(
+"int main(int argc, char *argv[])
+ {
+     volatile int tmp[argc];
+     tmp[0] = argv[0][0];
+     return tmp[0];
+ }"
+HAVE_C99_VLA)
+
+
 # Add definitions, compiler switches, etc.
 INCLUDE_DIRECTORIES("${OpenAL_SOURCE_DIR}/include" "${OpenAL_BINARY_DIR}")
 IF(CMAKE_VERSION VERSION_LESS "2.8.8")
@@ -302,8 +313,10 @@ ENDIF()
 CHECK_C_SOURCE_COMPILES("int foo(const char *str, ...) __attribute__((format(printf, 1, 2)));
                          int main() {return 0;}" HAVE_GCC_FORMAT)
 
+IF(NOT HAVE_C99_VLA)
+    CHECK_INCLUDE_FILE(alloca.h HAVE_ALLOCA_H)
+ENDIF()
 CHECK_INCLUDE_FILE(malloc.h HAVE_MALLOC_H)
-CHECK_INCLUDE_FILE(alloca.h HAVE_ALLOCA_H)
 CHECK_INCLUDE_FILE(strings.h HAVE_STRINGS_H)
 CHECK_INCLUDE_FILE(cpuid.h HAVE_CPUID_H)
 CHECK_INCLUDE_FILE(sys/sysconf.h HAVE_SYS_SYSCONF_H)
@@ -327,18 +340,20 @@ CHECK_SYMBOL_EXISTS(aligned_alloc    stdlib.h HAVE_ALIGNED_ALLOC)
 CHECK_SYMBOL_EXISTS(posix_memalign   stdlib.h HAVE_POSIX_MEMALIGN)
 CHECK_SYMBOL_EXISTS(_aligned_malloc  malloc.h HAVE__ALIGNED_MALLOC)
 CHECK_SYMBOL_EXISTS(lrintf math.h HAVE_LRINTF)
-IF(HAVE_ALLOCA_H)
-    CHECK_SYMBOL_EXISTS(alloca alloca.h HAVE_ALLOCA)
-ELSEIF(HAVE_MALLOC_H)
-    CHECK_SYMBOL_EXISTS(alloca malloc.h HAVE_ALLOCA)
-ENDIF()
-IF(NOT HAVE_ALLOCA)
-    CHECK_SYMBOL_EXISTS(_alloca malloc.h HAVE__ALLOCA)
-    IF(NOT HAVE__ALLOCA)
-        MESSAGE(FATAL_ERROR "No alloca function found, please report!")
+IF(NOT HAVE_C99_VLA)
+    IF(HAVE_ALLOCA_H)
+        CHECK_SYMBOL_EXISTS(alloca alloca.h HAVE_ALLOCA)
+    ELSEIF(HAVE_MALLOC_H)
+        CHECK_SYMBOL_EXISTS(alloca malloc.h HAVE_ALLOCA)
     ENDIF()
+    IF(NOT HAVE_ALLOCA)
+        CHECK_SYMBOL_EXISTS(_alloca malloc.h HAVE__ALLOCA)
+        IF(NOT HAVE__ALLOCA)
+            MESSAGE(FATAL_ERROR "No alloca function found, please report!")
+        ENDIF()
 
-    ADD_DEFINITIONS(-Dalloca=_alloca)
+        ADD_DEFINITIONS(-Dalloca=_alloca)
+    ENDIF()
 ENDIF()
 
 IF(HAVE_FLOAT_H)
diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h
index 04514b5e..3d1f062a 100644
--- a/OpenAL32/Include/alMain.h
+++ b/OpenAL32/Include/alMain.h
@@ -314,6 +314,12 @@ typedef ptrdiff_t ALsizeiptrEXT;
 #define FORCE_ALIGN
 #endif
 
+#ifdef HAVE_C99_VLA
+#define DECL_VLA(T, _name, _size)  T _name[(_size)]
+#else
+#define DECL_VLA(T, _name, _size)  T *_name = alloca((_size) * sizeof(T))
+#endif
+
 #ifndef PATH_MAX
 #ifdef MAX_PATH
 #define PATH_MAX MAX_PATH
diff --git a/OpenAL32/sample_cvt.c b/OpenAL32/sample_cvt.c
index a4c59d9d..903ec8ca 100644
--- a/OpenAL32/sample_cvt.c
+++ b/OpenAL32/sample_cvt.c
@@ -917,10 +917,9 @@ static void Convert_##T##_ALima4(T *dst, const ALima4 *src, ALuint numchans,  \
                                  ALuint len, ALuint align)                    \
 {                                                                             \
     ALsizei byte_align = ((align-1)/2 + 4) * numchans;                        \
+    DECL_VLA(ALshort, tmp, align*numchans);                                   \
     ALuint i, j, k;                                                           \
-    ALshort *tmp;                                                             \
                                                                               \
-    tmp = alloca(align*numchans*sizeof(*tmp));                                \
     for(i = 0;i < len;i += align)                                             \
     {                                                                         \
         DecodeIMA4Block(tmp, src, numchans, align);                           \
@@ -968,10 +967,9 @@ static void Convert_ALima4_##T(ALima4 *dst, const T *src, ALuint numchans,    \
     ALint sample[MAX_INPUT_CHANNELS] = {0,0,0,0,0,0,0,0};                     \
     ALint index[MAX_INPUT_CHANNELS] = {0,0,0,0,0,0,0,0};                      \
     ALsizei byte_align = ((align-1)/2 + 4) * numchans;                        \
+    DECL_VLA(ALshort, tmp, align*numchans);                                   \
     ALuint i, j, k;                                                           \
-    ALshort *tmp;                                                             \
                                                                               \
-    tmp = alloca(align*numchans*sizeof(*tmp));                                \
     for(i = 0;i < len;i += align)                                             \
     {                                                                         \
         for(j = 0;j < align;j++)                                              \
@@ -1020,10 +1018,9 @@ static void Convert_##T##_ALmsadpcm(T *dst, const ALmsadpcm *src,             \
                                     ALuint align)                             \
 {                                                                             \
     ALsizei byte_align = ((align-2)/2 + 7) * numchans;                        \
+    DECL_VLA(ALshort, tmp, align*numchans);                                   \
     ALuint i, j, k;                                                           \
-    ALshort *tmp;                                                             \
                                                                               \
-    tmp = alloca(align*numchans*sizeof(*tmp));                                \
     for(i = 0;i < len;i += align)                                             \
     {                                                                         \
         DecodeMSADPCMBlock(tmp, src, numchans, align);                        \
@@ -1071,10 +1068,9 @@ static void Convert_ALmsadpcm_##T(ALmsadpcm *dst, const T *src,               \
 {                                                                             \
     ALint sample[MAX_INPUT_CHANNELS] = {0,0,0,0,0,0,0,0};                     \
     ALsizei byte_align = ((align-2)/2 + 7) * numchans;                        \
+    DECL_VLA(ALshort, tmp, align*numchans);                                   \
     ALuint i, j, k;                                                           \
-    ALshort *tmp;                                                             \
                                                                               \
-    tmp = alloca(align*numchans*sizeof(*tmp));                                \
     for(i = 0;i < len;i += align)                                             \
     {                                                                         \
         for(j = 0;j < align;j++)                                              \
diff --git a/config.h.in b/config.h.in
index a0c11f36..c80a7d56 100644
--- a/config.h.in
+++ b/config.h.in
@@ -89,6 +89,9 @@
 /* Define to the size of a long long int type */
 #cmakedefine SIZEOF_LONG_LONG ${SIZEOF_LONG_LONG}
 
+/* Define if we have C99 variable-length array support */
+#cmakedefine HAVE_C99_VLA
+
 /* Define if we have GCC's destructor attribute */
 #cmakedefine HAVE_GCC_DESTRUCTOR