FreeType: don’t use usable_size() as deallocation size

Instead use C-level malloc()/free() so that the size doesn’t need
to be known during deallocation, since FreeType doesn’t provide it.

Hopefully fixes https://github.com/servo/servo/issues/19058

4 files changed, 37 insertions, 50 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 2962a40f119..2e3b0c19fcb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1447,7 +1447,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "jemalloc-sys"
-version = "0.1.3"
+version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1456,10 +1456,10 @@ dependencies = [
 
 [[package]]
 name = "jemallocator"
-version = "0.1.3"
+version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "jemalloc-sys 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "jemalloc-sys 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.23 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -2391,7 +2391,7 @@ dependencies = [
  "heartbeats-simple 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "influent 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ipc-channel 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "jemalloc-sys 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "jemalloc-sys 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.23 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "profile_traits 0.0.1",
@@ -2956,8 +2956,9 @@ dependencies = [
 name = "servo_allocator"
 version = "0.0.1"
 dependencies = [
- "jemallocator 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "jemallocator 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.23 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -3912,8 +3913,8 @@ dependencies = [
 "checksum ipc-channel 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c10ed089b1921b01ef342c736a37ee0788eeb9a5f373bb2df1ba88d01125064f"
 "checksum itertools 0.5.10 (registry+https://github.com/rust-lang/crates.io-index)" = "4833d6978da405305126af4ac88569b5d71ff758581ce5a987dbfa3755f694fc"
 "checksum itoa 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "eb2f404fbc66fd9aac13e998248505e7ecb2ad8e44ab6388684c5fb11c6c251c"
-"checksum jemalloc-sys 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "94fb624d7e8345e5c42caab8d1db6ec925fdadff3fd0cb7dd781b41be8442828"
-"checksum jemallocator 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "1850725977c344d63af66e8fd00857646e3ec936c490cd63667860b7b03ab5c1"
+"checksum jemalloc-sys 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "479294d130502fada93c7a957e8d059b632b03d6204aca37af557dee947f30a9"
+"checksum jemallocator 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "28b211ca65c440322b6d4d9b5b850b01e8e298393b7ebcb8205b7cbb14ea6329"
 "checksum jpeg-decoder 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "2805ccb10ffe4d10e06ef68a158ff94c255211ecbae848fbde2146b098f93ce7"
 "checksum js 0.1.6 (git+https://github.com/servo/rust-mozjs)" = "<none>"
 "checksum kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7507624b29483431c0ba2d82aece8ca6cdba9382bff4ddd0f7490560c056098d"
diff --git a/components/allocator/Cargo.toml b/components/allocator/Cargo.toml
index fccec48a5e9..645815ba1f1 100644
--- a/components/allocator/Cargo.toml
+++ b/components/allocator/Cargo.toml
@@ -11,8 +11,11 @@ path = "lib.rs"
 [features]
 unstable = ["kernel32-sys", "jemallocator"]
 
+[dependencies]
+libc = "0.2"  # Only used when 'unstable' is disabled, but looks like Cargo cannot express that.
+
 [target.'cfg(not(windows))'.dependencies]
-jemallocator = { version = "0.1.3", optional = true }
+jemallocator = { version = "0.1.4", optional = true }
 
 [target.'cfg(windows)'.dependencies]
 kernel32-sys = { version = "0.2.1", optional = true }
diff --git a/components/allocator/lib.rs b/components/allocator/lib.rs
index e832e485575..6c248f08055 100644
--- a/components/allocator/lib.rs
+++ b/components/allocator/lib.rs
@@ -9,9 +9,9 @@
 
 #[cfg(feature = "unstable")]
 #[global_allocator]
-static ALLOC: platform::Allocator = platform::Allocator;
+static ALLOC: Allocator = Allocator;
 
-pub use platform::usable_size;
+pub use platform::*;
 
 
 #[cfg(all(feature = "unstable", not(windows)))]
@@ -25,6 +25,11 @@ mod platform {
     pub unsafe extern "C" fn usable_size(ptr: *const c_void) -> usize {
         jemallocator::usable_size(ptr)
     }
+
+    /// Memory allocation APIs compatible with libc
+    pub mod libc_compat {
+        pub use super::jemallocator::ffi::{malloc, realloc, free};
+    }
 }
 
 #[cfg(all(feature = "unstable", windows))]
@@ -57,6 +62,10 @@ mod platform {
     pub unsafe extern "C" fn usable_size(_ptr: *const c_void) -> usize {
         0
     }
-}
-
 
+    /// Memory allocation APIs compatible with libc
+    pub mod libc_compat {
+        extern crate libc;
+        pub use self::libc::{malloc, realloc, free};
+    }
+}
diff --git a/components/gfx/platform/freetype/font_context.rs b/components/gfx/platform/freetype/font_context.rs
index f4a0745eb2c..2238561ba9c 100644
--- a/components/gfx/platform/freetype/font_context.rs
+++ b/components/gfx/platform/freetype/font_context.rs
@@ -9,8 +9,8 @@ use freetype::freetype::FT_Memory;
 use freetype::freetype::FT_MemoryRec_;
 use freetype::freetype::FT_New_Library;
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+use servo_allocator::libc_compat::{malloc, realloc, free};
 use servo_allocator::usable_size;
-use std::mem;
 use std::os::raw::{c_long, c_void};
 use std::ptr;
 use std::rc::Rc;
@@ -22,64 +22,38 @@ pub struct User {
     size: usize,
 }
 
-// FreeType doesn't require any particular alignment for allocations.
-const FT_ALIGNMENT: usize = 1;
-
 extern fn ft_alloc(mem: FT_Memory, req_size: c_long) -> *mut c_void {
-    assert!(FT_ALIGNMENT == 1);
-    let mut vec = Vec::<u8>::with_capacity(req_size as usize);
-    let ptr = vec.as_mut_ptr() as *mut c_void;
-    mem::forget(vec);
-
     unsafe {
-        let actual_size = usable_size(ptr as *const _);
+        let ptr = malloc(req_size as usize);
+        let ptr = ptr as *mut c_void;  // libc::c_void vs std::os::raw::c_void
+        let actual_size = usable_size(ptr);
         let user = (*mem).user as *mut User;
         (*user).size += actual_size;
+        ptr
     }
-
-    ptr
 }
 
 extern fn ft_free(mem: FT_Memory, ptr: *mut c_void) {
     unsafe {
-        let actual_size = usable_size(ptr as *const _);
+        let actual_size = usable_size(ptr);
         let user = (*mem).user as *mut User;
         (*user).size -= actual_size;
-
-        assert!(FT_ALIGNMENT == 1);
-        mem::drop(Vec::<u8>::from_raw_parts(ptr as *mut u8, actual_size, 0))
+        free(ptr as *mut _);
     }
 }
 
 extern fn ft_realloc(mem: FT_Memory, _old_size: c_long, new_req_size: c_long,
                      old_ptr: *mut c_void) -> *mut c_void {
-    let old_actual_size;
-    let mut vec;
-    unsafe {
-        old_actual_size = usable_size(old_ptr as *const _);
-        let old_size = old_actual_size as usize;
-        vec = Vec::<u8>::from_raw_parts(old_ptr as *mut u8, old_size, old_size);
-    };
-
-    let new_req_size = new_req_size as usize;
-    if new_req_size > old_actual_size {
-        vec.reserve_exact(new_req_size - old_actual_size)
-    } else if new_req_size < old_actual_size {
-        vec.truncate(new_req_size);
-        vec.shrink_to_fit()
-    }
-
-    let new_ptr = vec.as_mut_ptr() as *mut c_void;
-    mem::forget(vec);
-
     unsafe {
-        let new_actual_size = usable_size(new_ptr as *const _);
+        let old_actual_size = usable_size(old_ptr);
+        let new_ptr = realloc(old_ptr as *mut _, new_req_size as usize);
+        let new_ptr = new_ptr as *mut c_void;
+        let new_actual_size = usable_size(new_ptr);
         let user = (*mem).user as *mut User;
         (*user).size += new_actual_size;
         (*user).size -= old_actual_size;
+        new_ptr
     }
-
-    new_ptr
 }
 
 // A |*mut User| field in a struct triggers a "use of `#[derive]` with a raw pointer" warning from