Index: uspace/lib/posix/include/posix/float.h
===================================================================
--- uspace/lib/posix/include/posix/float.h	(revision 0262f1807e11a032ab437d75fec302582b513c09)
+++ uspace/lib/posix/include/posix/float.h	(revision c84f1a4616689e52888bfae446f99c0344d5b268)
@@ -36,5 +36,49 @@
 #define POSIX_FLOAT_H_
 
-/* Empty. Just to satisfy preprocessor. */
+/*
+ * The macros defined below are needed for compilation of MPFR
+ * (http://www.mpfr.org/). Probably, they should be provided by GCC
+ * itself but that does not work for cross-compilation.
+ *
+ * They are intentionally guarded by the given macro to ensure that anyone
+ * who wants them states this explicitly.
+ *
+ * The values are the ones GCC prints when compiled on i686 Linux.
+ *
+ * WARNING: the values are not accurate (especially the long double ones)!
+ *
+ */
+#ifdef FLOAT_H_YES_I_REALLY_WANT_LIMITS
+
+/* float limits */
+#define FLT_MIN 1.1754943508222875079687365372222456778186655567720875215087517062784172594547271728515625e-38
+#define FLT_MAX 340282346638528859811704183484516925440
+
+/* double limits */
+#define DBL_MIN 2.2250738585072013830902327173324040642192159804623318305533274168872044348139181958542831590125110205640673397310358110051524341615534601088560123853777188211307779935320023304796101474425836360719216e-308
+#define DBL_MAX 1.7976931348623157081452742373170435679807056752584499659891747680315726078002853876058955863276687817154045895351438246423432132688946418276846754670353751698604991057655128207624549009038932894407587e+308
+
+/* long double limits */
+#define LDBL_MIN 3.3621031431120935062626778173217526025980793448464712401088272298087426993907289670430927063650562228625019066688234732270901114717276781407474941951906317291667263914849985862188944930687409323125832e-4932L
+#define LDBL_MAX 1.1897314953572317650212638530309702051690633222946242004403237338917370055229707226164102903365288828535456978074955773144274431536702884341981255738537436786735932007069732632019159182829615243655295e+4932L
+
+/* epsilons */
+#define FLT_EPSILON 1.1920928955078125e-07
+#define DBL_EPSILON 2.220446049250313080847263336181640625e-16
+#define LDBL_EPSILON 1.08420217248550443400745280086994171142578125e-19L
+
+/* float radix */
+#define FLT_RADIX 2
+
+/* mantisa */
+#define FLT_MANT_DIG 24
+#define DBL_MANT_DIG 53
+#define LDBL_MANT_DIG 64
+
+/* exponents */
+#define DBL_MIN_EXP -1021
+#define DBL_MAX_EXP 1024
+
+#endif
 
 #endif /* POSIX_FLOAT_H_ */