Disable FP exceptions in H5T init code (#3837)

The H5T floating-point datatype initialization code can raise exceptions when handling signaling NaNs. This change disables FE_INVALID exceptions during initialization.

Also removes the -ieee=full change for NAG Fortran as that shouldn't be necessary anymore.

Fixes #3831

4 files changed, 54 insertions, 28 deletions

diff --git a/config/linux-gnulibc1 b/config/linux-gnulibc1
index 92f2be6..b4139ee 100644
--- a/config/linux-gnulibc1
+++ b/config/linux-gnulibc1
@@ -183,10 +183,7 @@ case $FC_BASENAME in
     nagfor)
 
         F9XSUFFIXFLAG=""
-        # NOTE: The default is -ieee=stop, which will cause problems
-        #       when the H5T module performs floating-point type
-        #       introspection
-        AM_FCFLAGS="$AM_FCFLAGS -ieee=full"
+        AM_FCFLAGS="$AM_FCFLAGS"
         FSEARCH_DIRS=""
 
         # Production
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 5e85378..1454574 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -408,6 +408,22 @@ Bug Fixes since HDF5-1.14.0 release
 ===================================
     Library
     -------
+    - Suppressed floating-point exceptions in H5T init code
+
+      The floating-point datatype initialization code in H5Tinit_float.c
+      could raise FE_INVALID exceptions while munging bits and performing
+      comparisons that might involve NaN. This was not a problem when the
+      initialization code was executed in H5detect at compile time (prior
+      to 1.14.3), but now that the code is executed at library startup
+      (1.14.3+), these exceptions can be caught by user code, as is the
+      default in the NAG Fortran compiler.
+
+      Starting in 1.14.4, we now suppress floating-point exceptions while
+      initializing the floating-point types and clear FE_INVALID before
+      restoring the original environment.
+
+      Fixes GitHub #3831
+
     - Fixed a file handle leak in the core VFD
 
       When opening a file with the core VFD and a file image, if the file
@@ -1190,12 +1206,6 @@ Known Problems
     -O1 for the time being:
     https://forums.developer.nvidia.com/t/hdf5-no-longer-compiles-with-nv-23-9/269045.
 
-    IEEE standard arithmetic enables software to raise exceptions such as overflow,
-    division by zero, and other illegal operations without interrupting or halting
-    the program flow. The HDF5 C library intentionally performs these exceptions.
-    Therefore, the "-ieee=full" nagfor switch is necessary when compiling a program
-    to avoid stopping on an exception.
-
     CMake files do not behave correctly with paths containing spaces.
     Do not use spaces in paths because the required escaping for handling spaces
     results in very complex and fragile build files.
diff --git a/src/H5Tinit_float.c b/src/H5Tinit_float.c
index 3b9e127..3213f00 100644
--- a/src/H5Tinit_float.c
+++ b/src/H5Tinit_float.c
@@ -51,19 +51,23 @@
  * Function:    DETECT_F
  *
  * Purpose:     This macro takes a floating point type like `double' and
- *              a base name like `natd' and detects byte order, mantissa
- *              location, exponent location, sign bit location, presence or
- *              absence of implicit mantissa bit, and exponent bias and
- *              initializes a detected_t structure with those properties.
+ *              and detects byte order, mantissa location, exponent location,
+ *              sign bit location, presence or absence of implicit mantissa
+ *              bit, and exponent bias and initializes a detected_t structure
+ *              with those properties.
+ *
+ *              Note that these operations can raise floating-point
+ *              exceptions and building with some compiler options
+ *              (especially Fortran) can cause problems.
  *-------------------------------------------------------------------------
  */
-#define DETECT_F(TYPE, VAR, INFO)                                                                            \
+#define DETECT_F(TYPE, INFO)                                                                                 \
     do {                                                                                                     \
-        TYPE          _v1, _v2, _v3;                                                                         \
-        unsigned char _buf1[sizeof(TYPE)], _buf3[sizeof(TYPE)];                                              \
-        unsigned char _pad_mask[sizeof(TYPE)];                                                               \
-        unsigned char _byte_mask;                                                                            \
-        int           _i, _j, _last = (-1);                                                                  \
+        TYPE    _v1, _v2, _v3;                                                                               \
+        uint8_t _buf1[sizeof(TYPE)], _buf3[sizeof(TYPE)];                                                    \
+        uint8_t _pad_mask[sizeof(TYPE)];                                                                     \
+        uint8_t _byte_mask;                                                                                  \
+        int     _i, _j, _last = -1;                                                                          \
                                                                                                              \
         memset(&INFO, 0, sizeof(INFO));                                                                      \
         INFO.size = sizeof(TYPE);                                                                            \
@@ -81,7 +85,7 @@
         _v1 = (TYPE)4.0L;                                                                                    \
         H5MM_memcpy(_buf1, (const void *)&_v1, sizeof(TYPE));                                                \
         for (_i = 0; _i < (int)sizeof(TYPE); _i++)                                                           \
-            for (_byte_mask = (unsigned char)1; _byte_mask; _byte_mask = (unsigned char)(_byte_mask << 1)) { \
+            for (_byte_mask = (uint8_t)1; _byte_mask; _byte_mask = (uint8_t)(_byte_mask << 1)) {             \
                 _buf1[_i] ^= _byte_mask;                                                                     \
                 H5MM_memcpy((void *)&_v2, (const void *)_buf1, sizeof(TYPE));                                \
                 H5_GCC_CLANG_DIAG_OFF("float-equal")                                                         \
@@ -118,7 +122,7 @@
         _v1 = (TYPE)1.0L;                                                                                    \
         _v2 = (TYPE)-1.0L;                                                                                   \
         if (H5T__bit_cmp(sizeof(TYPE), INFO.perm, &_v1, &_v2, _pad_mask, &(INFO.sign)) < 0)                  \
-            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "failed to detect byte order");                    \
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "failed to determine sign bit");                   \
                                                                                                              \
         /* Mantissa */                                                                                       \
         INFO.mpos = 0;                                                                                       \
@@ -126,12 +130,11 @@
         _v1 = (TYPE)1.0L;                                                                                    \
         _v2 = (TYPE)1.5L;                                                                                    \
         if (H5T__bit_cmp(sizeof(TYPE), INFO.perm, &_v1, &_v2, _pad_mask, &(INFO.msize)) < 0)                 \
-            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "failed to detect byte order");                    \
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "failed to determine mantissa");                   \
         INFO.msize += 1 + (unsigned)(INFO.imp ? 0 : 1) - INFO.mpos;                                          \
                                                                                                              \
         /* Exponent */                                                                                       \
-        INFO.epos = INFO.mpos + INFO.msize;                                                                  \
-                                                                                                             \
+        INFO.epos  = INFO.mpos + INFO.msize;                                                                 \
         INFO.esize = INFO.sign - INFO.epos;                                                                  \
                                                                                                              \
         _v1        = (TYPE)1.0L;                                                                             \
@@ -456,17 +459,24 @@ H5T__set_precision(H5T_fpoint_det_t *d)
 herr_t H5_NO_UBSAN
 H5T__init_native_float_types(void)
 {
+    fenv_t           saved_fenv;
     H5T_fpoint_det_t det;
     H5T_t           *dt        = NULL;
     herr_t           ret_value = SUCCEED;
 
     FUNC_ENTER_PACKAGE
 
+    /* Turn off floating-point exceptions while initializing to avoid
+     * tripping over signaling NaNs while looking at "don't care" bits.
+     */
+    if (feholdexcept(&saved_fenv) != 0)
+        HSYS_GOTO_ERROR(H5E_DATATYPE, H5E_CANTSET, FAIL, "can't save floating-point environment");
+
     /* H5T_NATIVE_FLOAT */
 
     /* Get the type's characteristics */
     memset(&det, 0, sizeof(H5T_fpoint_det_t));
-    DETECT_F(float, FLOAT, det);
+    DETECT_F(float, det);
 
     /* Allocate and fill type structure */
     if (NULL == (dt = H5T__alloc()))
@@ -497,7 +507,7 @@ H5T__init_native_float_types(void)
 
     /* Get the type's characteristics */
     memset(&det, 0, sizeof(H5T_fpoint_det_t));
-    DETECT_F(double, DOUBLE, det);
+    DETECT_F(double, det);
 
     /* Allocate and fill type structure */
     if (NULL == (dt = H5T__alloc()))
@@ -528,7 +538,7 @@ H5T__init_native_float_types(void)
 
     /* Get the type's characteristics */
     memset(&det, 0, sizeof(H5T_fpoint_det_t));
-    DETECT_F(long double, LDOUBLE, det);
+    DETECT_F(long double, det);
 
     /* Allocate and fill type structure */
     if (NULL == (dt = H5T__alloc()))
@@ -561,6 +571,14 @@ H5T__init_native_float_types(void)
     H5T_native_order_g = det.order;
 
 done:
+    /* Clear any FE_INVALID exceptions from NaN handling */
+    if (feclearexcept(FE_INVALID) != 0)
+        HSYS_GOTO_ERROR(H5E_DATATYPE, H5E_CANTSET, FAIL, "can't clear floating-point exceptions");
+
+    /* Restore the original environment */
+    if (feupdateenv(&saved_fenv) != 0)
+        HSYS_GOTO_ERROR(H5E_DATATYPE, H5E_CANTSET, FAIL, "can't restore floating-point environment");
+
     if (ret_value < 0) {
         if (dt != NULL) {
             dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
diff --git a/src/H5private.h b/src/H5private.h
index 14a0ac3..3aaa0d5 100644
--- a/src/H5private.h
+++ b/src/H5private.h
@@ -26,6 +26,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <fenv.h>
 #include <float.h>
 #include <math.h>
 #include <setjmp.h>