From: Waldemar Kozaczuk <[email protected]>
Committer: Nadav Har'El <[email protected]>
Branch: master

Add libc aliases to some mathematical functions

Some libraries like x265 fmpeg codec are linked
to reference libc aliases of some math functions like
log*, exp and pow ones. Unfortunately because our
versions of these funcions are provided by musl
and we do not modify musl code we cannot
add aliases by simple weak_alias construct.

Therefore we add a simple stub file in libc
where we define functions with alias names that delegate
to corresponding functions provided by musl.

Another alternative would be to copy corresponding
files from musl to libc directory and add weak_alias there.
This would be slightly more performant as we would avoid
unnecessary instructions involved in calling a function.

Signed-off-by: Waldemar Kozaczuk <[email protected]>
Message-Id: <[email protected]>

---
diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -1302,6 +1302,7 @@ musl += math/tgammal.o
 musl += math/trunc.o
 musl += math/truncf.o
 musl += math/truncl.o
+libc += math/aliases.o

 # Issue #867: Gcc 4.8.4 has a bug where it optimizes the trivial round-
 # related functions incorrectly - it appears to convert calls to any
diff --git a/libc/math/aliases.c b/libc/math/aliases.c
--- a/libc/math/aliases.c
+++ b/libc/math/aliases.c
@@ -0,0 +1,26 @@
+#include "libm.h"
+
+double __exp_finite(double x)
+{
+       return exp(x);
+}
+
+double __log10_finite(double x)
+{
+       return log10(x);
+}
+
+double __log2_finite(double x)
+{
+       return log2(x);
+}
+
+double __log_finite(double x)
+{
+       return log(x);
+}
+
+double __pow_finite(double x, double y)
+{
+       return pow(x, y);
+}

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