Tweak how std is pulled in for gimli

Try to fix a namespacing conflict found when testing libstd.

Cargo.toml

@@ -70,7 +70,7 @@ std = []
 # be affected by feature selection here. Also note that it's highly unlikely you
 # want to configure this. If you're having trouble getting backtraces it's
 # likely best to open an issue.
-gimli-symbolize = ["addr2line", "miniz_oxide", "object", "std"]
+gimli-symbolize = ["addr2line", "miniz_oxide", "object"]
 libbacktrace = ["backtrace-sys/backtrace-sys"]
 
 #=======================================

src/symbolize/gimli.rs

@@ -16,15 +16,17 @@ use core::convert::TryInto;
 use core::mem;
 use core::u32;
 use libc::c_void;
-use std::ffi::OsString;
-use std::fs::File;
-use std::path::Path;
-use std::prelude::v1::*;
+use mystd::ffi::OsString;
+use mystd::fs::File;
+use mystd::path::Path;
+use mystd::prelude::v1::*;
 
 #[cfg(backtrace_in_libstd)]
-mod std {
+mod mystd {
     pub use crate::*;
 }
+#[cfg(not(backtrace_in_libstd))]
+extern crate std as mystd;
 
 #[cfg(windows)]
 #[path = "gimli/mmap_windows.rs"]
@@ -97,7 +99,7 @@ cfg_if::cfg_if! {
     if #[cfg(windows)] {
         use core::mem::MaybeUninit;
         use super::super::windows::*;
-        use std::os::windows::prelude::*;
+        use mystd::os::windows::prelude::*;
         use alloc::vec;
 
         mod coff;
@@ -187,8 +189,8 @@ cfg_if::cfg_if! {
         // macOS uses the Mach-O file format and uses DYLD-specific APIs to
         // load a list of native libraries that are part of the appplication.
 
-        use std::os::unix::prelude::*;
-        use std::ffi::{OsStr, CStr};
+        use mystd::os::unix::prelude::*;
+        use mystd::ffi::{OsStr, CStr};
 
         mod macho;
         use self::macho::Object;
@@ -340,8 +342,8 @@ cfg_if::cfg_if! {
         // and typically implement an API called `dl_iterate_phdr` to load
         // native libraries.
 
-        use std::os::unix::prelude::*;
-        use std::ffi::{OsStr, CStr};
+        use mystd::os::unix::prelude::*;
+        use mystd::ffi::{OsStr, CStr};
 
         mod elf;
         use self::elf::Object;
@@ -362,7 +364,7 @@ cfg_if::cfg_if! {
             let libs = &mut *(vec as *mut Vec<Library>);
             let name = if (*info).dlpi_name.is_null() || *(*info).dlpi_name == 0{
                 if libs.is_empty() {
-                    std::env::current_exe().map(|e| e.into()).unwrap_or_default()
+                    mystd::env::current_exe().map(|e| e.into()).unwrap_or_default()
                 } else {
                     OsString::new()
                 }
@@ -388,7 +390,7 @@ cfg_if::cfg_if! {
         // Everything else should use ELF, but doesn't know how to load native
         // libraries.
 
-        use std::os::unix::prelude::*;
+        use mystd::os::unix::prelude::*;
         mod elf;
         use self::elf::Object;