Use alloca for dynamic stack allocation

detomon · Dec 15, 2024 · 2f84cf4 · 2f84cf4
1 parent c1552be
commit 2f84cf4
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Showing 3 changed files with 14 additions and 3 deletions.
diff --git a/config.h.in b/config.h.in
@@ -3,6 +3,9 @@
 /* Defines SDL version */
 #undef BK_SDL_VERSION
 
+/* Define to 1 if you have the <alloca.h> header file. */
+#undef HAVE_ALLOCA_H
+
 /* Define to 1 if you have the <fcntl.h> header file. */
 #undef HAVE_FCNTL_H
 
@@ -13,6 +16,9 @@
    to 0 otherwise. */
 #undef HAVE_MALLOC
 
+/* Define to 1 if you have the <malloc.h> header file. */
+#undef HAVE_MALLOC_H
+
 /* Define to 1 if you have the <math.h> header file. */
 #undef HAVE_MATH_H
 

diff --git a/configure.ac b/configure.ac
@@ -2,7 +2,7 @@
 # Process this file with autoconf to produce a configure script.
 
 AC_PREREQ([2.61])
-AC_INIT([BlipKit],[0.17.6],[simon@monoxid.net],[blipkit],[https://blipkit.audio])
+AC_INIT([BlipKit], [0.17.6], [simon@monoxid.net], [blipkit], [https://blipkit.audio])
 
 AC_CONFIG_SRCDIR([src/BKBase.c])
 AC_CONFIG_HEADER([config.h])
@@ -35,7 +35,7 @@ AM_CFLAGS="$AM_CFLAGS -Wall \
 CHECK_COMPILE_FLAG([-std=c11], [AM_CFLAGS])
 
 # Checks for header files.
-AC_CHECK_HEADERS([fcntl.h math.h stdarg.h stddef.h stdint.h stdlib.h string.h unistd.h])
+AC_CHECK_HEADERS([alloca.h fcntl.h malloc.h math.h stdarg.h stddef.h stdint.h stdlib.h string.h unistd.h])
 
 AC_ARG_WITH([sdl],
 	AS_HELP_STRING([--without-sdl], [do not link agains SDL library]))

diff --git a/src/BKContext.c b/src/BKContext.c
@@ -23,6 +23,11 @@
 
 #include "BKContext.h"
 #include "BKUnit.h"
+#ifdef HAVE_ALLOCA_H // Assume GNU.
+#include <alloca.h>
+#elif HAVE_MALLOC_H // Assume MSVC.
+#include <malloc.h>
+#endif
 
 extern BKInt BKContextSetAttrInt(BKContext* ctx, BKEnum attr, BKInt value);
 
@@ -276,6 +281,7 @@ BKInt BKContextGenerate(BKContext* ctx, BKFrame outFrames[], BKUInt size) {
 
 BKInt BKContextGenerateToTime(BKContext* ctx, BKTime endTime, BKInt (*write)(BKFrame inFrames[], BKUInt size, void* info), void* info) {
 	BKInt numFrames = 0;
+	BKFrame* frames = (BKFrame*)alloca(sizeof(BKFrame) * ctx->numChannels * BK_MAX_GENERATE_SAMPLES);
 
 	while (BKTimeIsLess(ctx->currentTime, endTime)) {
 		BKTime deltaTime = BKTimeSub(endTime, ctx->currentTime);
@@ -293,7 +299,6 @@ BKInt BKContextGenerateToTime(BKContext* ctx, BKTime endTime, BKInt (*write)(BKF
 		// write frames if buffer filled or end time is reached
 		if (BKBufferSize(&ctx->channels[0]) >= BK_MAX_GENERATE_SAMPLES || BKTimeIsGreaterEqual(ctx->currentTime, endTime)) {
 			BKInt size;
-			BKFrame frames[ctx->numChannels * BK_MAX_GENERATE_SAMPLES];
 
 			size = BKContextRead(ctx, frames, BK_MAX_GENERATE_SAMPLES);
 			numFrames += size;