docs(embed/c): add minimal call-exported-function example

docs/embed/c/call_exported_function.md

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+---
+sidebar_position: 6
+---
+
+# Call an Exported Function
+
+This page shows the smallest useful C host that loads a WASM module and calls one exported function with the WasmEdge C API.
+
+Compared with the [C SDK introduction](intro.md), this example:
+
+- Does **not** enable WASI (the module below does not need it)
+- Takes the module path and input `n` from the command line
+- Shows how to link against a **user-local** WasmEdge install (`~/.local/wasmedge`)
+
+For AOT compilation and the full API surface, see [intro.md](intro.md) and the [C API reference](reference/latest.md).
+
+## Prerequisites
+
+1. [Install WasmEdge](../../start/install.md#install) (tested with **0.17.1**).
+2. A C compiler (`gcc` or `clang`).
+3. Optional: [WABT](https://github.com/WebAssembly/wabt) (`wat2wasm`) if you start from WAT instead of a ready `.wasm` file.
+
+## Get `fibonacci.wasm`
+
+The module used here is [examples/wasm/fibonacci.wat](https://github.com/WasmEdge/WasmEdge/blob/master/examples/wasm/fibonacci.wat) from the WasmEdge repository. Convert it with WABT:
+
+```bash
+wat2wasm fibonacci.wat -o fibonacci.wasm
+```
+
+Alternatively, copy a prebuilt `fibonacci.wasm` from a WasmEdge checkout under `examples/wasm/`.
+
+Check the export with the CLI reactor:
+
+```bash
+$ wasmedge --reactor fibonacci.wasm fib 8
+34
+```
+
+## Host program
+
+Save as `run_fib.c`:
+
+```c
+#include <stdio.h>
+#include <stdlib.h>
+#include <wasmedge/wasmedge.h>
+
+int main(int Argc, const char *Argv[]) {
+  if (Argc < 3) {
+    printf("Usage: %s <wasm file> <n>\n", Argv[0]);
+    return 1;
+  }
+
+  int32_t N = (int32_t)atoi(Argv[2]);
+  WasmEdge_VMContext *VMCxt = WasmEdge_VMCreate(NULL, NULL);
+  WasmEdge_Value Params[1] = {WasmEdge_ValueGenI32(N)};
+  WasmEdge_Value Returns[1];
+  WasmEdge_String FuncName = WasmEdge_StringCreateByCString("fib");
+
+  WasmEdge_Result Res = WasmEdge_VMRunWasmFromFile(
+      VMCxt, Argv[1], FuncName, Params, 1, Returns, 1);
+
+  if (WasmEdge_ResultOK(Res)) {
+    printf("fib(%d) = %d\n", N, WasmEdge_ValueGetI32(Returns[0]));
+  } else {
+    printf("Error: %s\n", WasmEdge_ResultGetMessage(Res));
+  }
+
+  WasmEdge_StringDelete(FuncName);
+  WasmEdge_VMDelete(VMCxt);
+  return WasmEdge_ResultOK(Res) ? 0 : 1;
+}
+```
+
+Flow:
+
+1. `WasmEdge_VMCreate` — create a VM (configure/store may be `NULL`)
+2. `WasmEdge_ValueGenI32` — pack the `i32` argument
+3. `WasmEdge_VMRunWasmFromFile` — load the module and call `fib`
+4. Read the result, then delete the string and VM
+
+## Build and run
+
+If WasmEdge is on the default library path:
+
+```bash
+gcc run_fib.c -lwasmedge -o run_fib
+./run_fib fibonacci.wasm 8
+```
+
+Expected output:
+
+```text
+fib(8) = 34
+```
+
+If you installed WasmEdge under `~/.local/wasmedge` (common for the official tarball on Linux), point the compiler at `include` and `lib64`:
+
+```bash
+WASMEDGE_ROOT="$HOME/.local/wasmedge"
+
+gcc run_fib.c \
+  -I"$WASMEDGE_ROOT/include" \
+  -L"$WASMEDGE_ROOT/lib64" -lwasmedge \
+  -Wl,-rpath,"$WASMEDGE_ROOT/lib64" \
+  -o run_fib
+
+./run_fib fibonacci.wasm 8
+./run_fib fibonacci.wasm 32
+```
+
+```text
+fib(8) = 34
+fib(32) = 3524578
+```
+
+<!-- prettier-ignore -->
+:::note
+On some Linux systems an older `libwasmedge` from the distro package may still be present under `/usr/lib`. Prefer the install you intend to use with `-L` / `-rpath` (or uninstall the package version) so the host links against the matching headers and shared library.
+:::
+
+## Related
+
+- [WasmEdge C SDK Introduction](intro.md) — same `fib` example with WASI enabled, plus AOT
+- [Use WasmEdge Library](library.md) — headers and linking details
+- [C API reference](reference/latest.md)