Update the locale thread-safely.

setlocale() affects the entire process, potentially changing the locale
while another thread is executing.  In POSIX.1-2008, a thread-safe
uselocale() function was added that affects only the current thread.
Use this function instead when it's available.

Author: Tavian Barnes

svm.cpp

@@ -7,7 +7,13 @@
 #include <stdarg.h>
 #include <limits.h>
 #include <locale.h>
+
+#if __unix__
+#	include <unistd.h> // For _POSIX_VERSION
+#endif
+
 #include "svm.h"
+
 int libsvm_version = LIBSVM_VERSION;
 typedef float Qfloat;
 typedef signed char schar;
@@ -2638,16 +2644,55 @@ static const char *kernel_type_table[]=
 	"linear","polynomial","rbf","sigmoid","precomputed",NULL
 };
 
-int svm_save_model(const char *model_file_name, const svm_model *model)
+#if _POSIX_VERSION >= 200809L
+
+// If possible, use the thread-safe uselocale() function
+typedef locale_t locale_handle;
+
+static locale_handle set_c_locale()
 {
-	FILE *fp = fopen(model_file_name,"w");
-	if(fp==NULL) return -1;
+	locale_handle c_locale = newlocale(LC_ALL_MASK, "C", 0);
+	locale_handle old_locale = uselocale(c_locale);
+	return old_locale;
+}
+
+static void restore_locale(locale_handle locale)
+{
+	locale_handle c_locale = uselocale(locale);
+	if (c_locale && c_locale != LC_GLOBAL_LOCALE) {
+		freelocale(c_locale);
+	}
+}
+
+#else
+
+// But fall back to setlocale() if uselocale() is not available
+typedef char *locale_handle;
 
-	char *old_locale = setlocale(LC_ALL, NULL);
+static locale_handle set_c_locale()
+{
+	locale_handle old_locale = setlocale(LC_ALL, NULL);
 	if (old_locale) {
 		old_locale = strdup(old_locale);
 	}
 	setlocale(LC_ALL, "C");
+	return old_locale;
+}
+
+static void restore_locale(locale_handle locale)
+{
+	setlocale(LC_ALL, locale);
+	free(locale);
+}
+
+#endif
+
+int svm_save_model(const char *model_file_name, const svm_model *model)
+{
+	FILE *fp = fopen(model_file_name,"w");
+	if(fp==NULL) return -1;
+
+	locale_handle old_locale = set_c_locale();
 
 	const svm_parameter& param = model->param;
 
@@ -2728,8 +2773,7 @@ int svm_save_model(const char *model_file_name, const svm_model *model)
 		fprintf(fp, "\n");
 	}
 
-	setlocale(LC_ALL, old_locale);
-	free(old_locale);
+	restore_locale(old_locale);
 
 	if (ferror(fp) != 0 || fclose(fp) != 0) return -1;
 	else return 0;
@@ -2878,11 +2922,7 @@ svm_model *svm_load_model(const char *model_file_name)
 	FILE *fp = fopen(model_file_name,"rb");
 	if(fp==NULL) return NULL;
 
-	char *old_locale = setlocale(LC_ALL, NULL);
-	if (old_locale) {
-		old_locale = strdup(old_locale);
-	}
-	setlocale(LC_ALL, "C");
+	locale_handle old_locale = set_c_locale();
 
 	// read parameters
 
@@ -2898,8 +2938,7 @@ svm_model *svm_load_model(const char *model_file_name)
 	if (!read_model_header(fp, model))
 	{
 		fprintf(stderr, "ERROR: fscanf failed to read model\n");
-		setlocale(LC_ALL, old_locale);
-		free(old_locale);
+		restore_locale(old_locale);
 		free(model->rho);
 		free(model->label);
 		free(model->nSV);
@@ -2971,8 +3010,7 @@ svm_model *svm_load_model(const char *model_file_name)
 	}
 	free(line);
 
-	setlocale(LC_ALL, old_locale);
-	free(old_locale);
+	restore_locale(old_locale);
 
 	if (ferror(fp) != 0 || fclose(fp) != 0)
 		return NULL;