From 2669953fa599b064582aaadc67d092e5144709dd Mon Sep 17 00:00:00 2001
From: Kevin Boos <kevinaboos@gmail.com>
Date: Thu, 14 Oct 2021 18:35:58 -0700
Subject: [PATCH 1/6] Make the `write_core` and `write` features no_std
 compatible by no longer requiring the `std` feature. Note that the `write`
 feature could optionally enable `std`, if desired. Also, adjust the features
 required for example binaries.

---
 Cargo.toml                 |  7 ++++---
 crates/examples/Cargo.toml |  6 +++---
 src/lib.rs                 |  2 +-
 src/write/coff.rs          |  4 ++--
 src/write/elf/object.rs    |  2 +-
 src/write/elf/writer.rs    |  6 +++---
 src/write/macho.rs         |  2 +-
 src/write/mod.rs           | 15 +++++++++------
 src/write/pe.rs            |  6 +++---
 src/write/string.rs        |  8 ++++++--
 src/write/util.rs          |  9 ++++++---
 11 files changed, 39 insertions(+), 28 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 317dae3b..e87124f7 100755
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,11 +13,12 @@ description = "A unified interface for reading and writing object file formats."
 features = ['doc']
 
 [dependencies]
-crc32fast = { version = "1.2", optional = true }
+crc32fast = { version = "1.2", default-features = false, optional = true }
 flate2 = { version = "1", optional = true }
 indexmap = { version = "1.1", optional = true }
 wasmparser = { version = "0.57", optional = true }
 memchr = { version = "2.4.1", default-features = false }
+hashbrown = { version = "0.9.1", features = ["ahash"], default-features = false, optional = true }
 
 # Internal feature, only used when building as part of libstd, not part of the
 # stable interface of this crate.
@@ -34,7 +35,7 @@ read_core = []
 # Read support for all file formats (including unaligned files).
 read = ["read_core", "archive", "coff", "elf", "macho", "pe", "unaligned"]
 # Core write support. You will need to enable some file formats too.
-write_core = ["crc32fast", "indexmap/std", "std"]
+write_core = ["crc32fast", "indexmap", "hashbrown"]
 # Write support for all file formats.
 write = ["write_core", "coff", "elf", "macho", "pe"]
 
@@ -43,7 +44,7 @@ write = ["write_core", "coff", "elf", "macho", "pe"]
 
 # Enable things that require libstd.
 # Currently, this provides an `Error` implementation.
-std = ["memchr/std"]
+std = ["memchr/std", "indexmap/std", "crc32fast/std"]
 # Enable decompression of compressed sections.
 # This feature is not required if you want to do your own decompression.
 compression = ["flate2", "std"]
diff --git a/crates/examples/Cargo.toml b/crates/examples/Cargo.toml
index 43197389..2cc82366 100644
--- a/crates/examples/Cargo.toml
+++ b/crates/examples/Cargo.toml
@@ -24,11 +24,11 @@ required-features = ["object/read"]
 
 [[bin]]
 name = "elfcopy"
-required-features = ["object/read_core", "object/write_core", "object/elf"]
+required-features = ["object/read_core", "object/write_core", "object/elf", "object/std"]
 
 [[bin]]
 name = "elftoefi"
-required-features = ["object/read_core", "object/write_core", "object/elf", "object/pe"]
+required-features = ["object/read_core", "object/write_core", "object/elf", "object/pe", "object/std"]
 
 [[bin]]
 name = "objcopy"
@@ -48,7 +48,7 @@ required-features = ["object/read"]
 
 [[bin]]
 name = "pecopy"
-required-features = ["object/read_core", "object/write_core", "object/pe"]
+required-features = ["object/read_core", "object/write_core", "object/pe", "object/elf", "object/std"]
 
 [[bin]]
 name = "readobj"
diff --git a/src/lib.rs b/src/lib.rs
index 63c387d9..13eda90e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -73,7 +73,7 @@
 #[cfg(feature = "cargo-all")]
 compile_error!("'--all-features' is not supported; use '--features all' instead");
 
-#[cfg(feature = "read_core")]
+#[cfg(any(feature = "read_core", feature = "write_core"))]
 #[allow(unused_imports)]
 #[macro_use]
 extern crate alloc;
diff --git a/src/write/coff.rs b/src/write/coff.rs
index 5b6a27dc..486d667e 100644
--- a/src/write/coff.rs
+++ b/src/write/coff.rs
@@ -1,5 +1,5 @@
-use std::mem;
-use std::vec::Vec;
+use core::mem;
+use alloc::vec::Vec;
 
 use crate::endian::{LittleEndian as LE, U16Bytes, U32Bytes, U16, U32};
 use crate::pe as coff;
diff --git a/src/write/elf/object.rs b/src/write/elf/object.rs
index ffa09ffa..efcb8944 100644
--- a/src/write/elf/object.rs
+++ b/src/write/elf/object.rs
@@ -1,4 +1,4 @@
-use std::vec::Vec;
+use alloc::vec::Vec;
 
 use crate::elf;
 use crate::write::elf::writer::*;
diff --git a/src/write/elf/writer.rs b/src/write/elf/writer.rs
index eb815856..80740a29 100644
--- a/src/write/elf/writer.rs
+++ b/src/write/elf/writer.rs
@@ -1,7 +1,7 @@
 //! Helper for writing ELF files.
-use std::mem;
-use std::string::String;
-use std::vec::Vec;
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::mem;
 
 use crate::elf;
 use crate::endian::*;
diff --git a/src/write/macho.rs b/src/write/macho.rs
index 1aec4428..db4a1dab 100644
--- a/src/write/macho.rs
+++ b/src/write/macho.rs
@@ -1,4 +1,4 @@
-use std::mem;
+use core::mem;
 
 use crate::endian::*;
 use crate::macho;
diff --git a/src/write/mod.rs b/src/write/mod.rs
index 9113df08..21c1dc24 100644
--- a/src/write/mod.rs
+++ b/src/write/mod.rs
@@ -1,11 +1,12 @@
 //! Interface for writing object files.
 
-use std::borrow::Cow;
-use std::boxed::Box;
-use std::collections::HashMap;
-use std::string::String;
-use std::vec::Vec;
-use std::{error, fmt, io, result, str};
+use alloc::borrow::Cow;
+use hashbrown::HashMap;
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::{fmt, result, str};
+#[cfg(feature = "std")]
+use std::{error, io, boxed::Box};
 
 use crate::endian::{Endianness, U32, U64};
 use crate::{
@@ -42,6 +43,7 @@ impl fmt::Display for Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for Error {}
 
 /// The result type used within the write module.
@@ -551,6 +553,7 @@ impl<'a> Object<'a> {
     ///
     /// It is advisable to use a buffered writer like [`BufWriter`](std::io::BufWriter)
     /// instead of an unbuffered writer like [`File`](std::fs::File).
+    #[cfg(feature = "std")]
     pub fn write_stream<W: io::Write>(&self, w: W) -> result::Result<(), Box<dyn error::Error>> {
         let mut stream = StreamingBuffer::new(w);
         self.emit(&mut stream)?;
diff --git a/src/write/pe.rs b/src/write/pe.rs
index 27d03097..bbd29a72 100644
--- a/src/write/pe.rs
+++ b/src/write/pe.rs
@@ -1,7 +1,7 @@
 //! Helper for writing PE files.
-use std::mem;
-use std::string::String;
-use std::vec::Vec;
+use core::mem;
+use alloc::string::String;
+use alloc::vec::Vec;
 
 use crate::endian::{LittleEndian as LE, *};
 use crate::pe;
diff --git a/src/write/string.rs b/src/write/string.rs
index e596fb27..3bdfccca 100644
--- a/src/write/string.rs
+++ b/src/write/string.rs
@@ -1,5 +1,9 @@
-use indexmap::IndexSet;
-use std::vec::Vec;
+use alloc::vec::Vec;
+
+#[cfg(feature = "std")]
+type IndexSet<K> = indexmap::IndexSet<K>;
+#[cfg(not(feature = "std"))]
+type IndexSet<K> = indexmap::IndexSet<K, hashbrown::hash_map::DefaultHashBuilder>;
 
 /// An identifer for an entry in a string table.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
diff --git a/src/write/util.rs b/src/write/util.rs
index 02b96e47..51bc3515 100644
--- a/src/write/util.rs
+++ b/src/write/util.rs
@@ -1,6 +1,6 @@
-use std::io;
-use std::mem;
-use std::vec::Vec;
+use alloc::vec::Vec;
+#[cfg(feature = "std")]
+use std::{io, mem};
 
 use crate::pod::{bytes_of, bytes_of_slice, Pod};
 
@@ -86,6 +86,7 @@ impl WritableBuffer for Vec<u8> {
 ///
 /// It is advisable to use a buffered writer like [`BufWriter`](std::io::BufWriter)
 /// instead of an unbuffered writer like [`File`](std::fs::File).
+#[cfg(feature = "std")]
 #[derive(Debug)]
 pub struct StreamingBuffer<W> {
     writer: W,
@@ -93,6 +94,7 @@ pub struct StreamingBuffer<W> {
     result: Result<(), io::Error>,
 }
 
+#[cfg(feature = "std")]
 impl<W> StreamingBuffer<W> {
     /// Create a new `StreamingBuffer` backed by the given writer.
     pub fn new(writer: W) -> Self {
@@ -114,6 +116,7 @@ impl<W> StreamingBuffer<W> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<W: io::Write> WritableBuffer for StreamingBuffer<W> {
     #[inline]
     fn len(&self) -> usize {

From 524cded80f9dcf686d5c31c36de21f0ae1ada121 Mon Sep 17 00:00:00 2001
From: Kevin Boos <kevinaboos@gmail.com>
Date: Fri, 19 Nov 2021 11:10:12 -0800
Subject: [PATCH 2/6] Match the hashbrown version used by the existing
 `indexmap` dependency.

---
 Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Cargo.toml b/Cargo.toml
index e87124f7..0c03578f 100755
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,7 +18,7 @@ flate2 = { version = "1", optional = true }
 indexmap = { version = "1.1", optional = true }
 wasmparser = { version = "0.57", optional = true }
 memchr = { version = "2.4.1", default-features = false }
-hashbrown = { version = "0.9.1", features = ["ahash"], default-features = false, optional = true }
+hashbrown = { version = "0.11", features = ["ahash"], default-features = false, optional = true }
 
 # Internal feature, only used when building as part of libstd, not part of the
 # stable interface of this crate.

From 22c0fb0e380d4113497f96c0c671039d7b362bdd Mon Sep 17 00:00:00 2001
From: Kevin Boos <kevinaboos@gmail.com>
Date: Fri, 19 Nov 2021 11:48:14 -0800
Subject: [PATCH 3/6] Remove the unnecessary `elf` feature from the `pecopy`
 example binary's required features.

---
 crates/examples/Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/examples/Cargo.toml b/crates/examples/Cargo.toml
index 2cc82366..312d50fb 100644
--- a/crates/examples/Cargo.toml
+++ b/crates/examples/Cargo.toml
@@ -48,7 +48,7 @@ required-features = ["object/read"]
 
 [[bin]]
 name = "pecopy"
-required-features = ["object/read_core", "object/write_core", "object/pe", "object/elf", "object/std"]
+required-features = ["object/read_core", "object/write_core", "object/pe", "object/std"]
 
 [[bin]]
 name = "readobj"

From 62f317fefd6e5ecf1c7b43f89f041596f0b7c79d Mon Sep 17 00:00:00 2001
From: Kevin Boos <kevinaboos@gmail.com>
Date: Tue, 23 Nov 2021 11:54:40 -0800
Subject: [PATCH 4/6] * Separate the write-related std features into their own
 feature, `write_std`.

* Remove optional features from the `std` feature that were enabled unconditionally even if `write_core` wasn't enabled.

* Use the `hashbrown` `HashMap` implementation only if `std` is disabled, as before.
---
 Cargo.toml       | 4 +++-
 src/write/mod.rs | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 0c03578f..2032144c 100755
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -36,6 +36,8 @@ read_core = []
 read = ["read_core", "archive", "coff", "elf", "macho", "pe", "unaligned"]
 # Core write support. You will need to enable some file formats too.
 write_core = ["crc32fast", "indexmap", "hashbrown"]
+# Core write support with libstd features. You will need to enable some file formats too.
+write_std = ["write_core", "std", "indexmap/std", "crc32fast/std"]
 # Write support for all file formats.
 write = ["write_core", "coff", "elf", "macho", "pe"]
 
@@ -44,7 +46,7 @@ write = ["write_core", "coff", "elf", "macho", "pe"]
 
 # Enable things that require libstd.
 # Currently, this provides an `Error` implementation.
-std = ["memchr/std", "indexmap/std", "crc32fast/std"]
+std = ["memchr/std"]
 # Enable decompression of compressed sections.
 # This feature is not required if you want to do your own decompression.
 compression = ["flate2", "std"]
diff --git a/src/write/mod.rs b/src/write/mod.rs
index 21c1dc24..154c926b 100644
--- a/src/write/mod.rs
+++ b/src/write/mod.rs
@@ -1,12 +1,13 @@
 //! Interface for writing object files.
 
 use alloc::borrow::Cow;
-use hashbrown::HashMap;
 use alloc::string::String;
 use alloc::vec::Vec;
 use core::{fmt, result, str};
 #[cfg(feature = "std")]
-use std::{error, io, boxed::Box};
+use std::{boxed::Box, collections::HashMap, error, io};
+#[cfg(not(feature = "std"))]
+use hashbrown::HashMap;
 
 use crate::endian::{Endianness, U32, U64};
 use crate::{

From 3a6965b5517d5dbd9c786455107e2dd15a339e50 Mon Sep 17 00:00:00 2001
From: Kevin Boos <kevinaboos@gmail.com>
Date: Tue, 23 Nov 2021 17:13:58 -0800
Subject: [PATCH 5/6] * Make the `write` feature enable `write_std` by default,
 which leaves the behavior of `write` unchanged from the perspective of
 dependent crates. * Add the `write_std` feature to the `doc` generation
 feature. This could optionally just be `write`, too.

---
 Cargo.toml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 2032144c..c3cdf7c1 100755
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -38,8 +38,8 @@ read = ["read_core", "archive", "coff", "elf", "macho", "pe", "unaligned"]
 write_core = ["crc32fast", "indexmap", "hashbrown"]
 # Core write support with libstd features. You will need to enable some file formats too.
 write_std = ["write_core", "std", "indexmap/std", "crc32fast/std"]
-# Write support for all file formats.
-write = ["write_core", "coff", "elf", "macho", "pe"]
+# Write support for all file formats, including libstd features.
+write = ["write_std", "coff", "elf", "macho", "pe"]
 
 #=======================================
 # Misc features.
@@ -82,7 +82,7 @@ cargo-all = []
 #=======================================
 # Documentation should be generated with everything in "all" except for "unaligned".
 doc = [
-  "read_core", "write_core",
+  "read_core", "write_std",
   "std", "compression",
   "archive", "coff", "elf", "macho", "pe", "wasm",
 ]

From 97a86c5c7974a56afee7ff43da48fb0950b443f5 Mon Sep 17 00:00:00 2001
From: Kevin Boos <kevinaboos@gmail.com>
Date: Wed, 24 Nov 2021 10:28:07 -0800
Subject: [PATCH 6/6] Placate rustfmt

---
 src/write/coff.rs | 2 +-
 src/write/mod.rs  | 4 ++--
 src/write/pe.rs   | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/write/coff.rs b/src/write/coff.rs
index 486d667e..23684efa 100644
--- a/src/write/coff.rs
+++ b/src/write/coff.rs
@@ -1,5 +1,5 @@
-use core::mem;
 use alloc::vec::Vec;
+use core::mem;
 
 use crate::endian::{LittleEndian as LE, U16Bytes, U32Bytes, U16, U32};
 use crate::pe as coff;
diff --git a/src/write/mod.rs b/src/write/mod.rs
index 154c926b..d7c5132b 100644
--- a/src/write/mod.rs
+++ b/src/write/mod.rs
@@ -4,10 +4,10 @@ use alloc::borrow::Cow;
 use alloc::string::String;
 use alloc::vec::Vec;
 use core::{fmt, result, str};
-#[cfg(feature = "std")]
-use std::{boxed::Box, collections::HashMap, error, io};
 #[cfg(not(feature = "std"))]
 use hashbrown::HashMap;
+#[cfg(feature = "std")]
+use std::{boxed::Box, collections::HashMap, error, io};
 
 use crate::endian::{Endianness, U32, U64};
 use crate::{
diff --git a/src/write/pe.rs b/src/write/pe.rs
index bbd29a72..70da3a09 100644
--- a/src/write/pe.rs
+++ b/src/write/pe.rs
@@ -1,7 +1,7 @@
 //! Helper for writing PE files.
-use core::mem;
 use alloc::string::String;
 use alloc::vec::Vec;
+use core::mem;
 
 use crate::endian::{LittleEndian as LE, *};
 use crate::pe;