gcc/Linux fixes

.gitignore

@@ -26,6 +26,7 @@ ipch
 *.xcodeproj/
 obj*/
 !devtools/*.mak
+sp/src/devtools/makefile_base_posix.mak.link
 !utils/smdlexp/smdlexp.mak
 
 # Specific Source build products
@@ -87,3 +88,6 @@ sp/src/materialsystem/*.dll
 sp/src/materialsystem/*.pdb
 sp/src/vgui2/*.dll
 sp/src/vgui2/*.pdb
+
+# Build support files
+sp/src/devtools/gcc9+support.o

sp/src/devtools/gcc9+support.cpp

@@ -0,0 +1,59 @@
+// compatibility with old ABI
+#if __GNUC__ >= 9
+#include <cmath>
+
+extern "C" double __pow_finite(double a, double b)
+{
+	return pow(a, b);
+}
+
+extern "C" double __log_finite(double a)
+{
+	return log(a);
+}
+
+extern "C" double __exp_finite(double a)
+{
+	return exp(a);
+}
+
+extern "C" double __atan2_finite(double a, double b)
+{
+	return atan2(a, b);
+}
+
+extern "C" double __atan2f_finite(double a, double b)
+{
+	return atan2f(a, b);
+}
+
+extern "C" float __powf_finite(float a, float b)
+{
+	return powf(a, b);
+}
+
+extern "C" float __logf_finite(float a)
+{
+	return logf(a);
+}
+
+extern "C" float __expf_finite(float a)
+{
+	return expf(a);
+}
+
+extern "C" float __acosf_finite(float a)
+{
+	return acosf(a);
+}
+
+extern "C" double __asin_finite(double a)
+{
+	return asin(a);
+}
+
+extern "C" double __acos_finite(double a)
+{
+	return acos(a);
+}
+#endif