[lld][WebAssembly] Always search *.so for -Bdynamic #84288
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@llvm/pr-subscribers-lld-wasm @llvm/pr-subscribers-lld Author: YAMAMOTO Takashi (yamt) ChangesSearch *.so libraries regardless of -pie to make it a bit more straightforward to build non-pie dynamic-linked executables. Flip the default to -Bstatic as I think it's what most users expect for the default as of today. Full diff: https://github.com/llvm/llvm-project/pull/84288.diff 3 Files Affected:
diff --git a/lld/wasm/Config.h b/lld/wasm/Config.h
index 266348fef40316..c351e1cef10532 100644
--- a/lld/wasm/Config.h
+++ b/lld/wasm/Config.h
@@ -72,7 +72,7 @@ struct Configuration {
bool stripAll;
bool stripDebug;
bool stackFirst;
- bool isStatic = false;
+ bool isStatic = true;
bool trace;
uint64_t globalBase;
uint64_t initialHeap;
diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
index df7d4d1cc3d679..2599eca9389348 100644
--- a/lld/wasm/Driver.cpp
+++ b/lld/wasm/Driver.cpp
@@ -331,9 +331,7 @@ static std::optional<std::string> findFromSearchPaths(StringRef path) {
// search paths.
static std::optional<std::string> searchLibraryBaseName(StringRef name) {
for (StringRef dir : config->searchPaths) {
- // Currently we don't enable dynamic linking at all unless -shared or -pie
- // are used, so don't even look for .so files in that case..
- if (ctx.isPic && !config->isStatic)
+ if (!config->isStatic)
if (std::optional<std::string> s = findFile(dir, "lib" + name + ".so"))
return s;
if (std::optional<std::string> s = findFile(dir, "lib" + name + ".a"))
diff --git a/lld/wasm/Options.td b/lld/wasm/Options.td
index 70b5aadc26c2a0..7e954822ef6425 100644
--- a/lld/wasm/Options.td
+++ b/lld/wasm/Options.td
@@ -38,9 +38,9 @@ multiclass B<string name, string help1, string help2> {
// The following flags are shared with the ELF linker
def Bsymbolic: F<"Bsymbolic">, HelpText<"Bind defined symbols locally">;
-def Bdynamic: F<"Bdynamic">, HelpText<"Link against shared libraries (default)">;
+def Bdynamic: F<"Bdynamic">, HelpText<"Link against shared libraries">;
-def Bstatic: F<"Bstatic">, HelpText<"Do not link against shared libraries">;
+def Bstatic: F<"Bstatic">, HelpText<"Do not link against shared libraries (default)">;
def build_id: F<"build-id">, HelpText<"Alias for --build-id=fast">;
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Seems like a good change.
How about we keep -Bdynamic as the default when building with -shared and/or -pie ? It seems like in those modes we want to consume shared libraries by default.
Another alternative is that we always prefer shared libraries unless -static is passed? then it would be up to the clang driver (or users) to specify -static in the presence of both .so and .a files.
Ideally we would have some flag
it sounds reasonable to me.
as the latest wasi-sdk ships *.so files, i guess it surprises many users.
what do you mean? |
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In ELF linkers, -Bdynamic is the default. Clang Driver |
The problem is that dynamic linking under wasm is still experimental so we probably want to keep the default as static for now. IIUC we have several options for how to achieve "opt-in" dynamic linking:
The simplest option for now seem like (1). |
| @@ -72,7 +72,7 @@ struct Configuration { | |||
| bool stripAll; | |||
| bool stripDebug; | |||
| bool stackFirst; | |||
| bool isStatic = false; | |||
| bool isStatic = true; | |||
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Perhaps a comment: "Because dyamanic linking under Wasm is still experimental we default to static linking"
yes. it has been working for toywasm at least. |
Search *.so libraries regardless of -pie to make it a bit more straightforward to build non-pie dynamic-linked executables. Flip the default to -Bstatic as I think it's what most users expect for the default as of today. The assumption here is that, because dynamic-linking is not widely used for WebAssembly, the most users do not specify -Bdynamic or -Bstatic, expecting static link.
lld/wasm/Driver.cpp
Outdated
| // -Bdynamic by default if -pie or -shared is specified. | ||
| if (config->pie || config->shared) { | ||
| config->isStatic = false; | ||
| } |
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The convention removes braces in this single line statement case.
Search *.so libraries regardless of -pie to make it a bit more straightforward to build non-pie dynamic-linked executables.
Flip the default to -Bstatic as I think it's what most users expect for the default as of today.
The assumption here is that, because dynamic-linking is not widely used for WebAssembly, the most users do not specify -Bdynamic or -Bstatic, expecting static link.