simdutf: remove unused <iostream> from scalar/base64.h amalgamation - #320
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The vendored simdutf 8.2.0 amalgamation includes <iostream> in the scalar/base64.h section (simdutf_impl.h line 9949). The header is never used: simdutf's only iostream usage is gated behind SIMDUTF_LOGGING earlier in the file. Because SIMDUTF.h includes simdutf_impl.h and is pulled into every TU that needs simdutf (WTF's Base64.cpp, StringCommon.cpp, StringImpl.cpp, UTF8Conversion.cpp, SIMDUTF.cpp, and Bun's helpers.h), every one of those TUs emits an undefined reference to std::ios_base_library_init. That forces libstdc++'s globals_io.o into the final link, which in turn drags in locale_inst.cc, cxx11_locale_inst.cc, wlocale_inst.cc and cxx11_wlocale_inst.cc: roughly fifty static-initializer functions (std::ios_base::Init, std::locale::_S_initialize, and the full set of ctype/numpunct/moneypunct/timepunct/messages facets for char and wchar_t) that run before main on every Bun process. Upstream simdutf already removed both headers in simdutf/simdutf#962 (<iostream>) and simdutf/simdutf#979 (<algorithm>); this brings the vendored copy in line. Int128.cpp's <sstream>/<ostream> includes were also checked: they are used by UInt128ToFormattedString's std::ostringstream and the operator<<(ostream&, ...) overloads, and neither header emits the static ios_base::Init object, so they stay.
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When USE_BUN_JSC_ADDITIONS is on and the build type is not Debug, prepend Source/WTF/wtf/bun/BannedIncludes to the include search path so #include <iostream> resolves to a #error shim. This prevents a future WebKit or vendored-library change from reintroducing the reference to std::ios_base_library_init that drags globals_io.o (cin/cout/cerr/clog construction + the full std::locale facet set) into Bun's pre-main startup. Debug builds keep the real header, and -DBUN_ALLOW_IOSTREAM is the opt-out. <ostream>/<istream>/<sstream> are unaffected since they do not emit the static ios_base::Init object.
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Added a second commit that bans Companion Bun-side change (same shim for Bun's own C++ plus the bun-uws cleanup): oven-sh/bun#35256. |
![claude[bot]](https://avatars.githubusercontent.com/in/1236702?s=60&v=4){kind=small}
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Beyond the inline note, I also checked: the <algorithm> removal leaves std::min uses at simdutf_impl.h:1708/1755/13760 without a direct include, but <string> at :615 pulls it transitively on libstdc++/libc++ and upstream simdutf#979 already ships this way; the remaining <iostream> at :434 is correctly gated behind SIMDUTF_LOGGING; and the shim's #include_next (unsupported on MSVC) is only reachable via the BUN_ALLOW_IOSTREAM opt-out, so the default #error path is portable.
Extended reasoning...
Verified the two dropped includes against remaining uses in the amalgamation and confirmed the only other <iostream> is behind SIMDUTF_LOGGING. Checked the shim for MSVC portability — #include_next is a GCC/Clang extension but sits behind the opt-out macro, so Windows Release builds still get the intended #error. The gtest/TestWebKitAPI scope leak is covered by the inline comment; nothing further to add.
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| if(NOT CMAKE_BUILD_TYPE STREQUAL "Debug") | ||
| include_directories(BEFORE "${WTF_DIR}/wtf/bun/BannedIncludes") | ||
| endif() |
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🟡 This include_directories(BEFORE ...) runs at top-level project scope (OptionsJSCOnly.cmake is include()'d, not add_subdirectory()'d), so the <iostream> shim propagates to every target — including Source/ThirdParty/gtest and Tools/TestWebKitAPI, which are pulled in on non-Windows via ENABLE_API_TESTS ON. gtest unconditionally includes <iostream> (gtest-port.h:291, gtest.cc:52), so a plain ninja / cmake --build . (default all target) with -DUSE_BUN_JSC_ADDITIONS=ON in Release now fails on gtest-all.cc. All Bun CI/release paths build only --target jsc and are unaffected, but you may want to set(ENABLE_API_TESTS OFF) under USE_BUN_JSC_ADDITIONS, or add target_compile_definitions(gtest PRIVATE BUN_ALLOW_IOSTREAM), so the default target still builds.
Extended reasoning...
What breaks
The new include_directories(BEFORE "${WTF_DIR}/wtf/bun/BannedIncludes") is intended to shadow <iostream> for the WebKit sources that end up in the Bun link. However, it is applied at a scope that also covers third-party test code that legitimately uses iostreams, so building the default all target on non-Windows now fails.
Why the shim leaks to gtest
OptionsJSCOnly.cmake is not a subdirectory script — it is pulled in via include():
CMakeLists.txt:22→include(WebKitCommon)WebKitCommon.cmake:320→include(Options${PORT})
include() does not create a new directory scope, so the include_directories(BEFORE ...) call executes in the top-level CMakeLists.txt directory scope. Every add_subdirectory() that follows (starting with add_subdirectory(Source) at CMakeLists.txt:75) inherits it.
A few lines further down in this same file, ENABLE_API_TESTS is set ON for all non-Windows platforms. That causes:
Source/CMakeLists.txt:27-28→add_subdirectory(ThirdParty/gtest)Tools/CMakeLists.txt:24-26→add_subdirectory(TestWebKitAPI)
Neither of these is added with EXCLUDE_FROM_ALL, so both are part of the default all target. gtest's own CMakeLists.txt does not clear the inherited directory-level include list and does not define BUN_ALLOW_IOSTREAM. And gtest unconditionally includes <iostream>:
Source/ThirdParty/gtest/include/gtest/internal/gtest-port.h:291Source/ThirdParty/gtest/src/gtest.cc:52
Because the shim directory is added BEFORE and directory-level -I paths precede system include paths, #include <iostream> in gtest resolves to the shim and hits the #error.
Step-by-step reproduction
- On Linux or macOS, configure with
-DPORT=JSCOnly -DUSE_BUN_JSC_ADDITIONS=ON -DCMAKE_BUILD_TYPE=Release(orRelWithDebInfo). WTF_DIRis set byWebKitFS.cmake(included atWebKitCommon.cmake:308, i.e. beforeOptions${PORT}), so the shim path expands correctly.- Run
ninja(orcmake --build .) with no explicit target. - Ninja builds
gtest-all.cc, which#includesgtest.cc→#include <iostream>→ resolves toSource/WTF/wtf/bun/BannedIncludes/iostream→#error "<iostream> is banned in Bun WebKit release builds…". - Build fails.
Impact
Every documented and CI build path in this repo — Dockerfile*, build.ts, mac-release.bash, release.sh, windows-release.ps1 — invokes cmake --build … --target jsc (or --target artifact), which does not depend on gtest. So CI, autobuild artifacts, and the shipped Bun binaries are unaffected. This only bites a developer who runs a bare ninja / cmake --build . in a Release-flavored USE_BUN_JSC_ADDITIONS tree, and the #error message itself points at the -DBUN_ALLOW_IOSTREAM opt-out. It's a real regression in an ostensibly-supported configuration (this file is the one that sets ENABLE_API_TESTS ON), but not one that blocks the PR's goal.
Suggested fixes
Any one of:
set(ENABLE_API_TESTS OFF)inside theif(USE_BUN_JSC_ADDITIONS)block — Bun doesn't ship or run these tests anyway.- Add
target_compile_definitions(gtest PRIVATE BUN_ALLOW_IOSTREAM)(e.g. via aSource/ThirdParty/gtest/PlatformJSCOnly.cmake), and similarly for TestWebKitAPI. - Scope the shim to the libraries that actually feed the Bun link by using
target_include_directories(... BEFORE ...)onWTF/JavaScriptCore/bmallocinstead of the globalinclude_directories().
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robobun
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Jul 23, 2026
Picks up oven-sh/WebKit#320 (removes the stray <iostream> from the vendored simdutf amalgamation and bans <iostream> at compile time for non-Debug USE_BUN_JSC_ADDITIONS builds) and oven-sh/WebKit#322 (skip the eager timezone prewarm under USE_BUN_JSC_ADDITIONS). With this bump the release build's src/banned-includes/iostream shim no longer trips on the WebKit simdutf header, and no translation unit in the final link carries a reference to std::ios_base_library_init.
Jarred-Sumner
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Jul 24, 2026
## Problem Every Bun process runs libstdc++'s iostream and locale static initializers before `main`. From the release `bun-profile`: ``` _GLOBAL__sub_I.00090_globals_io.cc _GLOBAL__sub_I_cxx11_locale_inst.cc _GLOBAL__sub_I_cxx11_wlocale_inst.cc _GLOBAL__sub_I_locale_inst.cc _GLOBAL__sub_I_wlocale_inst.cc ``` `std::ios_base::Init`, `std::locale::_S_initialize`, `std::locale::_Impl`, and construction of ctype/numpunct/moneypunct/timepunct/messages for both `char` and `wchar_t`: roughly fifty functions out of libstdc++ that sit ahead of `main` in the `bun run orderfile` trace. Bun never uses C++ iostreams. ## Cause On libstdc++, `<iostream>` (and only `<iostream>`; not `<ostream>`/`<istream>`/`<sstream>`) emits an undefined reference to `_ZSt21ios_base_library_initv` in every TU that includes it. One such reference anywhere in the link pulls `globals_io.o` from libstdc++.a, whose initializer constructs `cin`/`cout`/`cerr`/`clog` and their `wchar_t` siblings, which in turn reference the full locale facet set. There are two sources: 1. **WebKit's vendored simdutf** (`Source/WTF/wtf/simdutf/simdutf_impl.h:9949`, an unused include in the `scalar/base64.h` section). Because `SIMDUTF.h` is included from `src/jsc/bindings/helpers.h`, ~70 Bun TUs carry the reference. Fixed in oven-sh/WebKit#320; upstream simdutf already dropped it in simdutf/simdutf#962. 2. **bun-uws headers**: `AsyncSocket.h`, `HttpRouter.h`, `Loop.h` include it without using it; `App.h`, `HttpContext.h`, `TopicTree.h` write fixed error strings via `std::cerr`. 7 Bun TUs carry the reference via `<bun-uws/src/App.h>`. ## Changes - `scripts/build/deps/webkit.ts`: bump `WEBKIT_VERSION` to `af2e8dc639` (oven-sh/WebKit#320: drop the simdutf `<iostream>` include and ban it at compile time for non-Debug `USE_BUN_JSC_ADDITIONS` builds; also picks up oven-sh/WebKit#321 lazy WebAssembly namespace and oven-sh/WebKit#322 skip eager timezone prewarm). Subsumes the `WEBKIT_VERSION` change in #35258. - `packages/bun-uws`: drop the `<iostream>` include from `AsyncSocket.h`, `HttpContext.h`, `HttpRouter.h`, `Loop.h`, `TopicTree.h`; delete the five `std::cerr << ...` validation messages (Bun validates these inputs before calling into uWS, so the paths are unreachable programmer errors and `std::terminate()` alone is enough). - `src/banned-includes/iostream`: a `#error` shim prepended to the `-I` search path for release builds. Any `#include <iostream>` in a Bun TU (including transitively from a WebKit header) fails the release compile with an explanation pointing here. Debug builds keep the real header for ad-hoc printf debugging; `-DBUN_ALLOW_IOSTREAM` is the opt-out. - `test/internal/source-lints/no-iostream-include.test.ts`: scans `src/`, `packages/bun-uws`, `packages/bun-usockets` for the include so debug CI also catches it. ## Verification With both oven-sh/WebKit#320 and this change applied to a release build: ``` nm build/release/bun-profile | grep ios_base4Init -> empty nm build/release/bun-profile | grep _S_initialize -> empty _GLOBAL__sub_I.00090_globals_io.cc gone bun-profile 547 KB smaller ``` Four `_GLOBAL__sub_I_*locale_inst.cc` stubs remain: these are the libstdc++ facet-id guard-byte initializers (a few dozen `movb $1,(%rax)` each) pulled by `Int128.cpp`'s `std::ostringstream`. `<sstream>` does not emit the static `Init` object and those stubs are near-free. ## Int128.cpp `Source/WTF/wtf/Int128.cpp` includes `<sstream>` and `<ostream>`. Both are load-bearing (`UInt128ToFormattedString`'s `std::ostringstream` and the `operator<<(std::ostream&, ...)` overloads) and neither emits the static `ios_base::Init` object, so they are left alone. <!-- robobun:evidence:begin --> --- **[decide:webkit]** gate passed · iteration 6 · 10 files touched <details><summary>fails on main (without fix)</summary> ```console ASAN without fix: 1 FAILED $ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/mechgate.xml" test/internal/source-lints/no-iostream-include.test.ts bun test v1.4.0 (eba02a1) test/internal/source-lints/no-iostream-include.test.ts: 45 | // root going away, which would make the ban below pass vacuously. 46 | expect(scanned).toBeGreaterThan(0); 47 | } 48 | 49 | violations.sort(); 50 | expect(violations).toEqual([]); ^ error: expect(received).toEqual(expected) - [] + [ + "packages/bun-uws/src/AsyncSocket.h", + "packages/bun-uws/src/HttpContext.h", + "packages/bun-uws/src/HttpRouter.h", + "packages/bun-uws/src/Loop.h", + "packages/bun-uws/src/TopicTree.h", + ] - Expected - 1 + Received + 7 at <anonymous> (/workspace/bun/test/internal/source-lints/no-iostream-include.test.ts:50:22) (fail) C++ sources compiled into Bun do not include <iostream> [748.19ms] 0 pass 1 fail 4 expect() calls Ran 1 test across 1 file. [3.00s] error: script "bd" exited with code 1 __F:1:S:0 release without fix: 1 FAILED bun test v1.4.0-canary.1 (507ab81) test/internal/source-lints/no-iostream-include.test.ts: 45 | // root going away, which would make the ban below pass vacuously. 46 | expect(scanned).toBeGreaterThan(0); 47 | } 48 | 49 | violations.sort(); 50 | expect(violations).toEqual([]); ^ error: expect(received).toEqual(expected) - [] + [ + "packages/bun-uws/src/AsyncSocket.h", + "packages/bun-uws/src/HttpContext.h", + "packages/bun-uws/src/HttpRouter.h", + "packages/bun-uws/src/Loop.h", + "packages/bun-uws/src/TopicTree.h", + ] - Expected - 1 + Received + 7 at <anonymous> (/workspace/bun/test/internal/source-lints/no-iostream-include.test.ts:50:22) (fail) C++ sources compiled into Bun do not include <iostream> [59.52ms] 0 pass 1 fail 4 expect() calls Ran 1 test across 1 file. [213.00ms] __F:1:S:0 ``` </details> <details><summary>passes on PR (with fix)</summary> ```console ASAN with fix: all passed $ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/mechgate.xml" test/internal/source-lints/no-iostream-include.test.ts bun test v1.4.0 (eba02a1) test/internal/source-lints/no-iostream-include.test.ts: (pass) C++ sources compiled into Bun do not include <iostream> [885.41ms] 1 pass 0 fail 4 expect() calls Ran 1 test across 1 file. [3.41s] __F:0:S:0 release with fix: all passed $ bun scripts/build.ts --profile=release [configured] bun-profile → bun (stripped) in 1174ms (unchanged) ninja: Entering directory `/workspace/bun/build/release' [0/1] reconfigure [0/13] cargo bun_bin → libbun_rust.a (--target x86_64-unknown-linux-gnu) nightly-2026-07-20-x86_64-unknown-linux-gnu unchanged - rustc 1.99.0-nightly (9f36de775 2026-07-19) �[1m�[92m Compiling�[0m bun_core v0.0.0 (/workspace/bun/src/bun_core) �[1m�[92m Compiling�[0m bun_errno v0.0.0 (/workspace/bun/src/errno) �[1m�[92m Compiling�[0m bun_ptr v0.0.0 (/workspace/bun/src/ptr) �[1m�[92m Compiling�[0m bun_boringssl_sys v0.0.0 (/workspace/bun/src/boringssl_sys) �[1m�[92m Compiling�[0m bun_safety v0.0.0 (/workspace/bun/src/safety) �[1m�[92m Compiling�[0m bun_zlib_sys v0.0.0 (/workspace/bun/src/zlib_sys) �[1m�[92m Compiling�[0m bun_cares_sys v0.0.0 (/workspace/bun/src/cares_sys) �[1m�[92m Compiling�[0m bun_zstd v0.0.0 (/workspace/bun/src/zstd) �[1m�[92m Compiling�[0m bun_picohttp v0.0.0 (/workspace/bun/src/picohttp) �[1m�[92m Compiling�[0m bun_output v0.0.0 (/workspace/bun/src/output) �[1m�[92m Compiling�[0m bun_clap v0.0.0 (/workspace/bun/src/clap) �[1m�[92m Compili ... (truncated) ``` </details> <details><summary>diff hotspot</summary> ``` packages/bun-uws/src/App.h | 3 -- packages/bun-uws/src/AsyncSocket.h | 1 - packages/bun-uws/src/HttpContext.h | 3 -- packages/bun-uws/src/HttpRouter.h | 1 - packages/bun-uws/src/Loop.h | 1 - packages/bun-uws/src/TopicTree.h | 5 --- scripts/build/deps/webkit.ts | 7 --- scripts/build/flags.ts | 6 +++ src/banned-includes/iostream | 27 ++++++++++++ .../source-lints/no-iostream-include.test.ts | 51 ++++++++++++++++++++++ 10 files changed, 84 insertions(+), 21 deletions(-) ``` </details> **gate history** · 8 passed · 1 rejected · iteration 6 <details><summary>evidence per changed file</summary> ``` file reads edits tests packages/bun-uws/src/App.h 4 3 0 packages/bun-uws/src/AsyncSocket.h 1 1 0 packages/bun-uws/src/HttpContext.h 2 2 0 packages/bun-uws/src/HttpRouter.h 1 1 0 packages/bun-uws/src/Loop.h 1 1 0 packages/bun-uws/src/TopicTree.h 4 4 0 scripts/build/deps/webkit.ts 2 3 0 scripts/build/flags.ts 1 1 0 src/banned-includes/iostream 0 1 0 test/internal/source-lints/no-iostream-include.test.ts 2 3 0 ``` </details> <!-- robobun:evidence:end --> --------- Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com> Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
liooil
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Aug 7, 2026
## Problem Every Bun process runs libstdc++'s iostream and locale static initializers before `main`. From the release `bun-profile`: ``` _GLOBAL__sub_I.00090_globals_io.cc _GLOBAL__sub_I_cxx11_locale_inst.cc _GLOBAL__sub_I_cxx11_wlocale_inst.cc _GLOBAL__sub_I_locale_inst.cc _GLOBAL__sub_I_wlocale_inst.cc ``` `std::ios_base::Init`, `std::locale::_S_initialize`, `std::locale::_Impl`, and construction of ctype/numpunct/moneypunct/timepunct/messages for both `char` and `wchar_t`: roughly fifty functions out of libstdc++ that sit ahead of `main` in the `bun run orderfile` trace. Bun never uses C++ iostreams. ## Cause On libstdc++, `<iostream>` (and only `<iostream>`; not `<ostream>`/`<istream>`/`<sstream>`) emits an undefined reference to `_ZSt21ios_base_library_initv` in every TU that includes it. One such reference anywhere in the link pulls `globals_io.o` from libstdc++.a, whose initializer constructs `cin`/`cout`/`cerr`/`clog` and their `wchar_t` siblings, which in turn reference the full locale facet set. There are two sources: 1. **WebKit's vendored simdutf** (`Source/WTF/wtf/simdutf/simdutf_impl.h:9949`, an unused include in the `scalar/base64.h` section). Because `SIMDUTF.h` is included from `src/jsc/bindings/helpers.h`, ~70 Bun TUs carry the reference. Fixed in oven-sh/WebKit#320; upstream simdutf already dropped it in simdutf/simdutf#962. 2. **bun-uws headers**: `AsyncSocket.h`, `HttpRouter.h`, `Loop.h` include it without using it; `App.h`, `HttpContext.h`, `TopicTree.h` write fixed error strings via `std::cerr`. 7 Bun TUs carry the reference via `<bun-uws/src/App.h>`. ## Changes - `scripts/build/deps/webkit.ts`: bump `WEBKIT_VERSION` to `af2e8dc639` (oven-sh/WebKit#320: drop the simdutf `<iostream>` include and ban it at compile time for non-Debug `USE_BUN_JSC_ADDITIONS` builds; also picks up oven-sh/WebKit#321 lazy WebAssembly namespace and oven-sh/WebKit#322 skip eager timezone prewarm). Subsumes the `WEBKIT_VERSION` change in #35258. - `packages/bun-uws`: drop the `<iostream>` include from `AsyncSocket.h`, `HttpContext.h`, `HttpRouter.h`, `Loop.h`, `TopicTree.h`; delete the five `std::cerr << ...` validation messages (Bun validates these inputs before calling into uWS, so the paths are unreachable programmer errors and `std::terminate()` alone is enough). - `src/banned-includes/iostream`: a `#error` shim prepended to the `-I` search path for release builds. Any `#include <iostream>` in a Bun TU (including transitively from a WebKit header) fails the release compile with an explanation pointing here. Debug builds keep the real header for ad-hoc printf debugging; `-DBUN_ALLOW_IOSTREAM` is the opt-out. - `test/internal/source-lints/no-iostream-include.test.ts`: scans `src/`, `packages/bun-uws`, `packages/bun-usockets` for the include so debug CI also catches it. ## Verification With both oven-sh/WebKit#320 and this change applied to a release build: ``` nm build/release/bun-profile | grep ios_base4Init -> empty nm build/release/bun-profile | grep _S_initialize -> empty _GLOBAL__sub_I.00090_globals_io.cc gone bun-profile 547 KB smaller ``` Four `_GLOBAL__sub_I_*locale_inst.cc` stubs remain: these are the libstdc++ facet-id guard-byte initializers (a few dozen `movb $1,(%rax)` each) pulled by `Int128.cpp`'s `std::ostringstream`. `<sstream>` does not emit the static `Init` object and those stubs are near-free. ## Int128.cpp `Source/WTF/wtf/Int128.cpp` includes `<sstream>` and `<ostream>`. Both are load-bearing (`UInt128ToFormattedString`'s `std::ostringstream` and the `operator<<(std::ostream&, ...)` overloads) and neither emits the static `ios_base::Init` object, so they are left alone. <!-- robobun:evidence:begin --> --- **[decide:webkit]** gate passed · iteration 6 · 10 files touched <details><summary>fails on main (without fix)</summary> ```console ASAN without fix: 1 FAILED $ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/mechgate.xml" test/internal/source-lints/no-iostream-include.test.ts bun test v1.4.0 (eba02a1f6) test/internal/source-lints/no-iostream-include.test.ts: 45 | // root going away, which would make the ban below pass vacuously. 46 | expect(scanned).toBeGreaterThan(0); 47 | } 48 | 49 | violations.sort(); 50 | expect(violations).toEqual([]); ^ error: expect(received).toEqual(expected) - [] + [ + "packages/bun-uws/src/AsyncSocket.h", + "packages/bun-uws/src/HttpContext.h", + "packages/bun-uws/src/HttpRouter.h", + "packages/bun-uws/src/Loop.h", + "packages/bun-uws/src/TopicTree.h", + ] - Expected - 1 + Received + 7 at <anonymous> (/workspace/bun/test/internal/source-lints/no-iostream-include.test.ts:50:22) (fail) C++ sources compiled into Bun do not include <iostream> [748.19ms] 0 pass 1 fail 4 expect() calls Ran 1 test across 1 file. [3.00s] error: script "bd" exited with code 1 __F:1:S:0 release without fix: 1 FAILED bun test v1.4.0-canary.1 (507ab8113) test/internal/source-lints/no-iostream-include.test.ts: 45 | // root going away, which would make the ban below pass vacuously. 46 | expect(scanned).toBeGreaterThan(0); 47 | } 48 | 49 | violations.sort(); 50 | expect(violations).toEqual([]); ^ error: expect(received).toEqual(expected) - [] + [ + "packages/bun-uws/src/AsyncSocket.h", + "packages/bun-uws/src/HttpContext.h", + "packages/bun-uws/src/HttpRouter.h", + "packages/bun-uws/src/Loop.h", + "packages/bun-uws/src/TopicTree.h", + ] - Expected - 1 + Received + 7 at <anonymous> (/workspace/bun/test/internal/source-lints/no-iostream-include.test.ts:50:22) (fail) C++ sources compiled into Bun do not include <iostream> [59.52ms] 0 pass 1 fail 4 expect() calls Ran 1 test across 1 file. [213.00ms] __F:1:S:0 ``` </details> <details><summary>passes on PR (with fix)</summary> ```console ASAN with fix: all passed $ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/mechgate.xml" test/internal/source-lints/no-iostream-include.test.ts bun test v1.4.0 (eba02a1f6) test/internal/source-lints/no-iostream-include.test.ts: (pass) C++ sources compiled into Bun do not include <iostream> [885.41ms] 1 pass 0 fail 4 expect() calls Ran 1 test across 1 file. [3.41s] __F:0:S:0 release with fix: all passed $ bun scripts/build.ts --profile=release [configured] bun-profile → bun (stripped) in 1174ms (unchanged) ninja: Entering directory `/workspace/bun/build/release' [0/1] reconfigure [0/13] cargo bun_bin → libbun_rust.a (--target x86_64-unknown-linux-gnu) nightly-2026-07-20-x86_64-unknown-linux-gnu unchanged - rustc 1.99.0-nightly (9f36de775 2026-07-19) �[1m�[92m Compiling�[0m bun_core v0.0.0 (/workspace/bun/src/bun_core) �[1m�[92m Compiling�[0m bun_errno v0.0.0 (/workspace/bun/src/errno) �[1m�[92m Compiling�[0m bun_ptr v0.0.0 (/workspace/bun/src/ptr) �[1m�[92m Compiling�[0m bun_boringssl_sys v0.0.0 (/workspace/bun/src/boringssl_sys) �[1m�[92m Compiling�[0m bun_safety v0.0.0 (/workspace/bun/src/safety) �[1m�[92m Compiling�[0m bun_zlib_sys v0.0.0 (/workspace/bun/src/zlib_sys) �[1m�[92m Compiling�[0m bun_cares_sys v0.0.0 (/workspace/bun/src/cares_sys) �[1m�[92m Compiling�[0m bun_zstd v0.0.0 (/workspace/bun/src/zstd) �[1m�[92m Compiling�[0m bun_picohttp v0.0.0 (/workspace/bun/src/picohttp) �[1m�[92m Compiling�[0m bun_output v0.0.0 (/workspace/bun/src/output) �[1m�[92m Compiling�[0m bun_clap v0.0.0 (/workspace/bun/src/clap) �[1m�[92m Compili ... (truncated) ``` </details> <details><summary>diff hotspot</summary> ``` packages/bun-uws/src/App.h | 3 -- packages/bun-uws/src/AsyncSocket.h | 1 - packages/bun-uws/src/HttpContext.h | 3 -- packages/bun-uws/src/HttpRouter.h | 1 - packages/bun-uws/src/Loop.h | 1 - packages/bun-uws/src/TopicTree.h | 5 --- scripts/build/deps/webkit.ts | 7 --- scripts/build/flags.ts | 6 +++ src/banned-includes/iostream | 27 ++++++++++++ .../source-lints/no-iostream-include.test.ts | 51 ++++++++++++++++++++++ 10 files changed, 84 insertions(+), 21 deletions(-) ``` </details> **gate history** · 8 passed · 1 rejected · iteration 6 <details><summary>evidence per changed file</summary> ``` file reads edits tests packages/bun-uws/src/App.h 4 3 0 packages/bun-uws/src/AsyncSocket.h 1 1 0 packages/bun-uws/src/HttpContext.h 2 2 0 packages/bun-uws/src/HttpRouter.h 1 1 0 packages/bun-uws/src/Loop.h 1 1 0 packages/bun-uws/src/TopicTree.h 4 4 0 scripts/build/deps/webkit.ts 2 3 0 scripts/build/flags.ts 1 1 0 src/banned-includes/iostream 0 1 0 test/internal/source-lints/no-iostream-include.test.ts 2 3 0 ``` </details> <!-- robobun:evidence:end --> --------- Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com> Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
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The vendored simdutf 8.2.0 amalgamation has an
#include <iostream>in thescalar/base64.hsection atSource/WTF/wtf/simdutf/simdutf_impl.h:9949. Nothing in that section uses iostreams; simdutf's only iostream use is already gated behindSIMDUTF_LOGGINGearlier in the same file.Why it matters
SIMDUTF.hincludessimdutf_impl.h, andSIMDUTF.his pulled in by:SIMDUTF.cpp,text/Base64.cpp,text/StringCommon.cpp,text/StringImpl.cpp,unicode/UTF8Conversion.cppsrc/jsc/bindings/helpers.h(transitively included by ~70 translation units),bun-simdutf.cpp, and several direct includesOn libstdc++ each of those TUs ends up with an undefined reference to
_ZSt21ios_base_library_initv, which pullsglobals_io.ofrom libstdc++.a into the link. That object carries the_GLOBAL__sub_I.00090_globals_io.ccinitializer (std::ios_base::Init) and transitively pullslocale_inst.cc,cxx11_locale_inst.cc,wlocale_inst.cc,cxx11_wlocale_inst.cc: roughly fifty functions of locale/facet construction (std::locale::_S_initialize,std::locale::_Impl, ctype/numpunct/moneypunct/timepunct/messages forcharandwchar_t) that run beforemainon every Bun process.From the release
bun-profilelinker map:Bun never uses C++ iostreams.
Change
Drop
<iostream>and<algorithm>from the amalgamatedscalar/base64.hsection. Upstream simdutf already removed both: simdutf/simdutf#962 dropped<iostream>and simdutf/simdutf#979 dropped<algorithm>. This just brings the vendored copy in line until the next simdutf bump.Verification
Standalone compile of
simdutf_impl.hwith the patch: builds cleanly,nmshows noios_baseor_GLOBAL__sub_Isymbols in the object. Same compile against the unpatched header emitsU _ZSt21ios_base_library_initv.After stripping the same undefined symbol from the five affected
libWTF.amembers and relinking Bun against the patched header,nm build/release/bun-profile | grep ios_base4Initis empty and the_GLOBAL__sub_I*_locale_inst.ccinitializers no longer appear (full relink result will be posted once the autobuild artifact is available).Int128.cpp
Source/WTF/wtf/Int128.cppincludes<sstream>and<ostream>. Both are load-bearing:UInt128ToFormattedStringusesstd::ostringstreamand theoperator<<(std::ostream&, {U,}Int128Impl)overloads are declared inInt128.h. Neither header defines the staticios_base::Initobject (only<iostream>does), so they do not contribute to pre-maininitialization and are left as-is.