Fix compatibility with glibc v2.42

Before checking a possible error of the strtol() function the 'errno'
have to be reset to zero.
Apparently there are situations in which 'errno' can be legally set
to a non-zaro value and this interferes with the error checking of
strtol().

Without the patch, the unit test suite stalls when it is executed in an
environment with glibc v2.42 and linux kernel < v6.13.

Patch kindly provided by Aurelien Jarno.
Original bub report:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1115531.

Author: avalentino

blosc/blosc2.c

@@ -2725,6 +2725,7 @@ int blosc2_compress(int clevel, int doshuffle, int32_t typesize,
   envvar = getenv("BLOSC_CLEVEL");
   if (envvar != NULL) {
     long value;
+    errno = 0; /* To distinguish success/failure after call */
     value = strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (value >= 0)) {
       clevel = (int)value;
@@ -2768,6 +2769,7 @@ int blosc2_compress(int clevel, int doshuffle, int32_t typesize,
   envvar = getenv("BLOSC_TYPESIZE");
   if (envvar != NULL) {
     long value;
+    errno = 0; /* To distinguish success/failure after call */
     value = strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (value > 0)) {
       typesize = (int32_t)value;
@@ -2790,6 +2792,7 @@ int blosc2_compress(int clevel, int doshuffle, int32_t typesize,
   envvar = getenv("BLOSC_BLOCKSIZE");
   if (envvar != NULL) {
     long blocksize;
+    errno = 0; /* To distinguish success/failure after call */
     blocksize = strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (blocksize > 0)) {
       blosc1_set_blocksize((size_t) blocksize);
@@ -2803,6 +2806,7 @@ int blosc2_compress(int clevel, int doshuffle, int32_t typesize,
   envvar = getenv("BLOSC_NTHREADS");
   if (envvar != NULL) {
     long nthreads;
+    errno = 0; /* To distinguish success/failure after call */
     nthreads = strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (nthreads > 0)) {
       result = blosc2_set_nthreads((int16_t) nthreads);
@@ -2986,6 +2990,7 @@ int blosc2_decompress(const void* src, int32_t srcsize, void* dest, int32_t dest
   /* Check for a BLOSC_NTHREADS environment variable */
   envvar = getenv("BLOSC_NTHREADS");
   if (envvar != NULL) {
+    errno = 0; /* To distinguish success/failure after call */
     nthreads = strtol(envvar, NULL, 10);
     if ((errno != EINVAL)) {
       if ((nthreads <= 0) || (nthreads > INT16_MAX)) {
@@ -4031,6 +4036,7 @@ blosc2_context* blosc2_create_cctx(blosc2_cparams cparams) {
   envvar = getenv("BLOSC_TYPESIZE");
   if (envvar != NULL) {
     int32_t value;
+    errno = 0; /* To distinguish success/failure after call */
     value = (int32_t) strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (value > 0)) {
       context->typesize = value;
@@ -4046,6 +4052,7 @@ blosc2_context* blosc2_create_cctx(blosc2_cparams cparams) {
   envvar = getenv("BLOSC_CLEVEL");
   if (envvar != NULL) {
     int value;
+    errno = 0; /* To distinguish success/failure after call */
     value = (int)strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (value >= 0)) {
       context->clevel = value;
@@ -4073,6 +4080,7 @@ blosc2_context* blosc2_create_cctx(blosc2_cparams cparams) {
   envvar = getenv("BLOSC_BLOCKSIZE");
   if (envvar != NULL) {
     int32_t blocksize;
+    errno = 0; /* To distinguish success/failure after call */
     blocksize = (int32_t) strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (blocksize > 0)) {
       context->blocksize = blocksize;
@@ -4086,6 +4094,7 @@ blosc2_context* blosc2_create_cctx(blosc2_cparams cparams) {
   /* Check for a BLOSC_NTHREADS environment variable */
   envvar = getenv("BLOSC_NTHREADS");
   if (envvar != NULL) {
+    errno = 0; /* To distinguish success/failure after call */
     int16_t nthreads = (int16_t) strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (nthreads > 0)) {
       context->nthreads = nthreads;
@@ -4174,6 +4183,7 @@ blosc2_context* blosc2_create_dctx(blosc2_dparams dparams) {
   context->nthreads = dparams.nthreads;
   char* envvar = getenv("BLOSC_NTHREADS");
   if (envvar != NULL) {
+    errno = 0; /* To distinguish success/failure after call */
     long nthreads = strtol(envvar, NULL, 10);
     if ((errno != EINVAL) && (nthreads > 0)) {
       context->nthreads = (int16_t) nthreads;